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Novel ternary intermetallic phase Ce2RuGe was synthesized via arc-melting of the constituents and subsequent annealing at 700°С. Its crystal structure was determined from the powder X-ray diffraction data collected at room temperature. The compound crystallizes in the orthorhombic structure of a new type: space group Pmmn (No. 59), lattice parameters: a = 4.38235(5) A, b = 4.31818(5) A, c = 9.91496(15) A, Z = 2, Pearson symbol oP8. In the fully ordered unit cell of Ce2RuGe, there are two crystallographic positions for Ce atoms, single site with Ru atoms, and single site with Ge atoms, each with the multiplicity of two. The crystal structure is built of infinite zigzag-like chains of the Ru and Ge atoms, propagating along the [010] direction. The essential feature is a very short interatomic distance between the Ce1 atoms and the Ru atoms being equal to 2.226(2) A, while the Ce2–Ru distance is of regular length. This structural property gives rise to distinctive physical behavior of the compound that exhibits the coexistence of valence fluctuations associated with unstable 4f shell of the Ce1 ions and a long-range magnetic ordering that emerges in the Ce2 ions sublattice. As revealed by means of magnetization, heat capacity and electrical resistivity measurements, Ce2RuGe orders antiferromagnetically at TN = 12.0(1) K, and becomes ferromagnetic below TC = 8.5(3) K.

We have studied phase equilibria in the silicon-rich part of the Yb–Pt–Si system. To this end, 22 alloys were prepared by a standard arc-melting process in an argon atmosphere and annealed at a temperature of 850°C. Physicochemical characterization of the samples included electron microscopy, X-ray microanalysis, X-ray diffraction, and differential thermal analysis. We have confirmed the existence of four previously known intermetallic compounds: YbPtSi, YbPt2Si2, Yb3Pt4Si6, and Yb2Pt3Si5. In addition, three new phases have been identified: YbPtSi2, Yb33Pt17Si50, and Yb11Pt33Si56. The structure type of the YbPtSi2 compound has been determined. We present statistical crystallographic data for the ternary phases and describe phase equilibria in the region studied in the 850°C isothermal section of the Yb–Pt–Si phase diagram.

Novel Ce-rich phases Ce 4 RuAl and Ce 23 Ru 7+ x Al 4- x (0 ≤ x ≤ 2.97) were found in the systematic investigation of the ternary Ce-Ru-Al system. Both compounds were investigated by scanning electron microscopy, EDX spectroscopy and X-ray diffraction methods. The Ce 4 RuAl compound crystallizes with a cubic structure of a Gd 4 RhIn type with lattice parameter a = 13.7709(8) A (sp. gr. F -43 m , Z = 16). Its crystal structure was determined from single crystal X-ray data (R F = 0.0241 for 741 independent reflections). The Ce 23 Ru 7+ x Al 4- x structure was established by X-ray powder diffraction. This compound belongs to Pr 23 Ir 7 Mg 4 structure type, space group P 6 3 mc . Cell parameters of Ce 23 Ru 7+ x Al 4- x at x = 0.4 are: a = 9.8137(4) A, c = 22.2010(13) A. In both compounds Ce 4 RuAl and Ce 23 Ru 7+ x Al 4- x some of the Ce-Ru distances are short, equal to 2.630 A and 2.562 A, respectively. Crystal chemistry of these intermetallics is characterized by packing of non-linear layers in which the Ru-centered trigonal [Ce 6 ] prisms are connected via common vertices and edges, - similar to packing in the related Ce 7 Ru 3 and La 15 Rh 5 Cd 2 compounds.

The crystal structure of the novel Al-rich intermetallic phase Ce4Pt9Al13 was determined from single-crystal X-ray diffraction data and confirmed by powder X-ray diffraction. The compound crystallizes with its own structure type, which is a “site exchange” variant of the Ho4Ir13Ge9-type (Pearson symbol oP52, space group Pmmn, No. 59, Z = 2, lattice parameters: a = 4.1826(1) A, b = 11.4424(3) A, c = 19.8475(5) A, V = 949.88(7) A3). The magnetic properties of Ce4Pt9Al13 were determined in the temperature range 1.72–400 K. Down to the lowest temperatures studied, the compound shows a Curie-Weiss paramagnetic behavior with strong crystalline electric field contribution observed below about 200 K. The electrical conductivity in Ce4Pt9Al13 has metallic character, and at low temperatures it is governed by an interplay of strong crystal field and Kondo interactions.

The formation of a ternary cerium germanide Ce4Rh4Ge3 was established. The crystal structure of this novel compound was determined by mean of single crystal and powder X-ray diffraction techniques to be of the monoclinic Nd4Rh4Ge3-type (space group C2/c, No.15, Pearson symbol mS44, Z = 4) with the lattice parameters: a = 21.027(6) A, b = 5.7248(16) A, c = 7.999(3) A, β = 110.39(3) deg. The low-temperature physical properties of Ce4Rh4Ge3 were studied by means of magnetic susceptibility, magnetization, heat capacity, electrical resistivity and magnetoresistance measurements. The compound was found to order ferromagnetically at TC = 4.2(2) K. Its physical behavior in the paramagnetic state was found to be governed by interplay of crystalline electric field effect and Kondo interactions, with possible contribution due to valence fluctuations associated with one of the two inequivalent cerium atoms located in the crystallographic unit cell of Ce4Rh4Ge3.

Ternary intermetallic alloys Ce 2 Rh 3+x Ge 1-x (0 ≤ x ≤ 0.33) have been found to crystallize in a rhombohedral structure of the Mg 2 Ni 3 Si-type (space group R -3 m ). With varying the stoichiometry, the lattice parameters significantly vary from a = 5.5887(2) A, c = 11.9557(5) A (hexagonal setting) for x = 0 to a = 5.5127(2) A, c = 12.2790(5) A for x = 0.33, while the unit cell volume remains nearly unchanged. By means of magnetic susceptibility, heat capacity and electrical resistivity measurements, the Ce 2 Rh 3+x Ge 1-x alloys have been shown to be intermediate valence systems with highly unstable 4 f shell of Ce ions. Notably, the ferromagnetic ordering, claimed in the literature to coexist with the valence fluctuations in Ce 2 Rh 3 Ge, has been revealed to be an extrinsic effect due to impurity contribution.

A novel ternary intermetallic germanide CeIrGe 2 has been studied by means of x-ray diffraction, magnetization, specific heat and electrical resistivity measurements, performed in wide ranges of temperature and external magnetic fields. The compound crystallizes in an orthorhombic structure of the CeNiSi 2 -type (space group Cmcm ). It exhibits a Kondo lattice behavior and orders antiferromagnetically at 4 K.

The novel cerium germanide Ce2IrGe3 was studied by means of x-ray diffraction, magnetic, electrical transport and heat capacity measurements. The compound was found to crystallize with slightly disordered hexagonal structure of Ce2CoSi3-type. The experimental results revealed that Ce2IrGe3 is a ferromagnetic-like Kondo lattice that orders at T C = 4 K .

Two novel ternary rare-earth aluminides, CePd 3 Al 2 and LaPd 3 Al 2 , were obtained by arc-melting the elements and subsequent annealing at 800 °C. Their crystal structures were determined from the single-crystal X-ray diffraction data. The compounds crystallize with their own structure type: space group Pnma , Z = 4, Pearson symbol oP 24, а = 7.491(2) A, b = 4.3575(17) A, ≿ = 13.123(4) A for CePd 3 Al 2 and а = 7.474(7) A, b = 4.3755(17) A, ≿ = 13.323(9) A for LaPd 3 Al 2 . The physical behavior of the Ce-based material was studied by means of magnetic, electrical resistivity and heat capacity measurements carried out down to 0.4 K. The compound was characterized as an antiferromagnetic heavy-fermion system with the Neel temperature T N = 1 K and the Kondo energy scale of about 2 K.

The new ternary intermetallic with high content of germanium, CeRuGe 5 , was found in the course of reinvestigation of the Ce-Ru-Ge system at 700 °C. The compound crystallizes in the tetragonal structure of new type (space group I 4/ mcm ) with the unit cell parameters: a = 6.1414(6) A, c = 13.751(3) A, Z = 4, Pearson symbol tI 28. The structure of CeRuGe 5 can be presented as [CeGe 3 ] and [RuGe 2 ] slabs alternating along the tetragonal c -axis. It is shown that the new structure of CeRuGe 5 and the known before structure of Sm 2 Ru 5 Ga 9 are derivatives from the common prototype – HoCoGa 5 . By means of magnetic, heat capacity and electrical transport measurements, the novel compound CeRuGe 5 was established to be a metallic Curie-Weiss paramagnet due to stable 4 f 1 electronic configuration of trivalent Ce ions. No intrinsic long-range magnetic ordering was found down to 1.7 K.

Phase relations in the ternary system Ce–Ir–Si have been established and the isothermal section at 950 °C was constructed based on X-ray powder diffraction, scanning electron microscopy, and electron probe microanalysis techniques on 83 alloys, which were prepared by arc melting under argon or powder reaction sintering. Among the 15 ternary compounds observed at 950 °C 8 phases have been reported earlier. Based on powder X-ray diffraction data the crystal structures for 6 new ternary phases were assigned to known structure types: τ6 – Ce3IrSi3 (Ta3B4-type), τ8 – Ce3Ir4Si4 (U3Ni4Si4-type), τ10 – Ce6Ir30Si19 (Sc6Co30Si19-type), τ12 – Ce2Ir12Si7 (Ho2Rh12As7-type), τ13 – Ce3Ir2−xSi2+x (Sm3Ir2Si2-type), and τ14 – Ce3Ir3Si2 (Ce3Rh3Si2-type). For another new compound τ1 – Ce4Ir27Si69 (at.%), which has homogeneity region along 27 at.% of Ir, the reflections were indexed in hexagonal lattice symmetry with cell parameters close to high-temperature IrSi3−x phase.

The crystal structure of Yb 2 PdGe 6 was studied by powder X-ray diffraction technique. The compound in both as-cast and annealed forms crystallizes with the orthorhombic structure of the Ce 2 GaGe 6 -type (space group Cmce ) that can be modelled as a sequence of AlB 2 -type slabs, quadrangular antiprismatic slabs, and distorted αPo-type slabs propagating along the crystallographic c direction. The low-temperature physical properties of Yb 2 PdGe 6 were determined by means of magnetic susceptibility and electrical resistivity measurements. The compound was characterized as an intermediate valent material because of a highly unstable 4 f shell of Yb ions.

A novel ternary compound Ce 3 RuSn 6 was synthesized as a single phase polycrystalline alloy. Its crystal structure was solved by direct methods and refined from the single crystal X-ray diffraction data down to R1 = 0.038 for 1021 independent reflections with I > 2σ(I) and 36 variable parameters. The compound crystallizes with an orthorhombic unit cell of the Yb 3 CoSn 6 type (space group Cmcm , lattice parameters: a = 4.6744 (4), b = 16.8542 (15), c = 13.3227 (12) A), in which Ce atoms occupy two independent crystallographic sites. Physical behavior in Ce 3 RuSn 6 was studied by means of magnetic susceptibility, electrical resistivity and heat capacity measurements, performed down to 0.4 K in magnetic fields up to 9 T. The compound exhibits ferromagnetic ordering below T C = 3 K. Its thermodynamic and electrical transport properties in the paramagnetic and ordered states are strongly influenced by Kondo effect with the characteristic temperature very close to T C .

New ternary intermetallic compound Ce2Ru2Al was prepared in polycrystalline form, and its crystal structure was determined from both powder and single crystal X-ray diffraction data. The aluminide was found to crystallize with an orthorhombic structure (space group Cmce) with the lattice parameters: a = 5.8914(4) A, b = 9.9603(6) A, and c = 6.9551(4) A. The derived unit cell is an ordered variant of the binary La2Ni3 type, where one of two Ni sites is fully occupied with Ru atoms, while another one accommodates Al atoms. The structure of Ce2Ru2Al can be regarded as a sequence of atomic layers normal to b-axis. The remarkable structural feature is a short distance between Ce and Ru atoms equal to 2.7816(4) A. Magnetic measurements revealed that Ce ions in Ce2Ru2Al possess unstable 4f shell that leads to intermediate valence behavior of the compound. Similar valence instability was observed before for other Ce intermetallics with short Ce–Ru bonds.

The aluminides CePd2Al2, CePd3Al3, and CePd4Al4 were synthesized and their properties studied by X-ray diffraction, magnetic, heat capacity, and electrical transport measurements. The crystal structures of CePd2Al2 and CePd4Al4 were determined and refined from the single-crystal X-ray diffraction data, while that of CePd3Al3 was designed by the trial-and-error method on the basis of crystal chemistry considerations and refined by the Rietveld method from the X-ray powder diffraction data. All three compounds were found to crystallize in the tetragonal space group P4/nmm with Z = 2. The lattice parameters of CePd2Al2 are a = 4.3974(9) Å and c = 9.871(4) Å. Those of CePd3Al3 are a = 4.3045(7) Å and c = 13.4426(18) Å, while those of CePd4Al4 are a = 4.325(2) Å and c = 16.230(5) Å. The structures represent a new homologous series built of structural units of the CaBe2Ge2- and CsCl-type. The three compounds were established to order antiferromagnetically at 2.5(1) K, 3.5(1) K, and 2.6(1) K for CePd2Al2, CePd3Al3, and CePd4Al4, respectively. All of them are Kondo lattices with the characteristic energy scale of 3-7 K.

The atomic order of the new polymorphic modification of the equiatomic stannide CeRuSn was established from single crystal X-ray diffraction data. The new modification of CeRuSn can be described as a superstructure of CeCoAl-type with tripling of the subcell along the c axis. Space group C 2/ m , lattice parameters a = 11.5702(12) A, b = 4.7529(5) A, c = 15.2414(16) A, β = 103.511(2)°, Z = 12. The structure was refined to R 1 = 0.034 for 1806 F 2 and 55 variables. The new modification has three independent crystallographic Ce sites, two of which form strongly shortened Ce–Ru contacts d Ce1 – Ru2 = 2.267 A, d Ce3 – Ru1 = 2.434 A and d Ce3 – Ru3 = 2.429 A.

The formation of novel ternary cerium germanide with the chemical composition Ce33.3Ir22.2Ge44.5 (at.%) was established. As derived from powder X-ray diffraction data, the compound crystallizes with two polymorphic modifications. The high-temperature modification, established for as-cast alloy, possesses a tetragonal ThSi2-type structure and can be named as Ce(IrxGe1-x)2, x = 0.32. The low-temperature modification forms in the course of heat treatment at 1073 K, crystallizes with an orthorhombic structure of its own type and can be labeled as Ce3Ir2-xGe4+x, x = 0.02. Both structures belong to the AlB2 structural family and are closely related to each other. In both modifications, statistical mixtures of Ir and Ge atoms occupy same crystallographic sites. As found by means of magnetization measurements, the two structural variants of Ce33.3Ir22.2Ge44.5 (at.%) exhibit very similar magnetic properties. Both polymorphs are Curie-Weiss paramagnets with strong crystalline electric field features observed at low temperatures.

The crystal structures of LaPd 2 Ge and LaPdGe 3 have been refined by X-ray diffraction on powdered polycrystalline samples. These ternaries crystallize in YPd 2 Si ( Pnma ) and BaNiSn 3 ( I 4 mm ) structure types, respectively. As revealed by electrical resistivity, thermoelectric power and specific heat measurements, the former compound is superconducting below 0.6 K, which is not the case for the latter one (at least down to 0.3 K). Moreover, LaPdGe 3 was found to be a typical metal in comparison to LaPd 2 Ge which is rather a semimetal.

Magnetic ordering in solid solutions of Cex(Gd,Pr,Nd,La)1-xNi is studied by measuring the DC magnetization and the AC susceptibility in the temperature range of 1.8–300 K. The valence state of ceriumions in Cex(Gd,Pr,Nd,La)1-xNi quasibinary systems is studied based on X-ray absorption spectra measured at synchrotron-radiation sources in the temperature range of 5–300 K. It is shown that chemical pressure and lowering the temperature help heighten the degree of delocalization of the 4f electrons of cerium in Cex(Gd, Nd, Pr)1-xNi systems. It is found that the substitution of magnetic ions (Gd, Pr, and Nd) with cerium results in significantly weaker magnetic-ordering suppression than the substitution of these ions with lanthanum at equal concentrations. The obtained data reveal the strong influence of cerium electrons on localized magnetism in the studied compounds. This effect is most probably associated with the contribution of partially delocalized 4f electrons of cerium to the exchange interaction.

The crystal structure of the novel intermetallic Yb ∼3 Pt ∼4 Si 6− x was determined by single crystal X-ray diffraction: space group P 2 1 / m (No. 11); a = 8.4560(3) A, b = 4.2109(2) A, c = 12.7864(5) A, β = 99.537(2)°, R F = 0.046, wR2 = 0.132. The title compound is a disordered variant of the Y 3 Pt 4 Ge 6 type. It is characterized by the intergrowth of slabs cut from the ThCr 2 Si 2 and YIrGe 2 types of structures.

In mixed-valence or heavy-fermion systems, the hybridization between local f orbitals and conduction band states can cause the suppression of long-range magnetic order, which competes with strong spin uctuations. Ce- and Yb-based systems have been found to exhibit fascinating physical properties (heavy-fermion superconductivity, non-Fermi-liquid states, etc.) when tuned to the vicinity of magnetic quantum critical points by use of various external control parameters (temperature, magnetic eld, chemical composition). Recently, similar effects (mixed-valence, Kondo uctuations, heavy Fermi liquid) have been reported to exist in some Eu-based compounds. Unlike Ce (Yb), Eu has a multiple electron (hole) occupancy of its 4f shell, and the magnetic Eu2+ state (4f7) has no orbital component in the usual LS coupling scheme, which can lead to a quite different and interesting physics. In the EuCu2(SixGe1-x)2 series, where the valence can be tuned by varying the Si/Ge ratio, it has been reported that a significant valence uctuation can exist even in the magnetic order regime. This paper presents a detailed study of the latter material using different microscopic probes (XANES, Mossbauer spectroscopy, elastic and inelastic neutron scattering), in which the composition dependence of the magnetic order and dynamics across the series is traced back to the changemore » in the Eu valence state. In particular, the results support the persistence of valence uctuations into the antiferromagnetic state over a sizable composition range below the critical Si concentration xc ≈ 0:65. In conclusion, the sequence of magnetic ground states in the series is shown to re ect the evolution of the magnetic spectral response.« less

The new title compound is synthesized by repeated arc melting of stoichiometric mixtures of the elements.

The crystal structure of Dy 2 PdGe 6 was studied by X-ray diffraction on single crystal. Space group Cmca (No. 64), a = 8.1337(16), b = 8.0208(16), c = 21.441(4) A, V = 1398.8 A 3 , Z = 8, 1259 unique reflections with I > 2 σ ( I 0 ) in refinement (2 Θ max = 75.81°), down to R 1 = 0.029, w R 2 = 0.071. The title compound represents an ordered derivative from the Ce 2 GaGe 6 -type. The crystal structure can be presented as a sequence of the AlB 2 -type slabs, quadrangular antiprisms slabs, and distorted αPo-type slabs along the c direction. The atomic order in Dy 2 PdGe 6 derived from the single crystal data was confirmed by X-ray powder diffraction with cell parameters a = 8.1348(6), b = 8.0145(5), c = 21.4396(14) A.

The crystal structure of the novel compound Ce 3 Rh 5 Si was solved by means of powder diffraction pattern analysis using the charge-flipping method. The refinements yielded the space group Pnma and the orthorhombic unit cell parameters: a = 1.52632(2) nm, b = 0.55092(1) nm, and c = 0.75302(1) nm. A characteristic feature of the crystal structure of Ce 3 Rh 5 Si are vertex-sharing [Rh 4 ] and [Rh 3 Si] tetrahedra, which form a three-dimensional framework with Ce atoms located inside truncated tetrahedral voids. The structure exhibits close relationship with those of CeRh 2 (MgCu 2 -type) and Ce 2 Rh 3 Si (Y 2 Rh 3 Si-type). Magnetic and electrical resistivity measurements of Ce 3 Rh 5 Si were performed down to 2 K. The compound was characterized as a Pauli paramagnet with metallic character of the electrical conductivity.

Polycrystalline samples of the intermetallic compounds Dy 2 PdGe 6 and La 2 PdGe 6 which crystallize in the orthorhombic structure ( Cmca space group) were studied by means of magnetic, electrical resistivity, specific heat and differential thermoelectric power measurements. The Dy-germanide is an antiferromagnet below 25(1) K and at low temperature and above magnetic fields of 3.5 T it exhibits a metamagnetic behaviour. Especially the specific heat measurements point to well-localized 4 f -electrons in this compound. Whereas the isostructural La-germanide is a nonmagnetic material taken here as a reference compound. A good overall fit of the resistivity to a general Bloch–Gruneisen formula indicates its metallic character in contrast to the Dy-germanide being a semimetallic-like conductor. For the latter compound in its ordered state the electrical resistvity, specific heat and thermoelectric power are dominated by electron–magnon scattering with antiferromagnetic spin-wave spectrum typical of anisotropic antiferromagnetic systems. The observed Schottky anomaly yields an assumed crystal field scheme of low-energy lying levels. Its thermoelectric power behaviour achieves medium positive values at high temperatures, indicating a hole domination in electrical transport properties. On the other hand, S ( T ) below T N for Dy- and in the whole temperatures measured for La-based compounds is negative, pointing to their electron carrier origin.

The crystal structure of the novel compound Yb3Pt23Si11 has been determined from powder X-ray diffraction data to be isotypic with cubic Ce3Pt23Si11 (space group F m 3 ¯ m ; a = 1.68052(5) nm). Magnetic susceptibility, electrical resistivity and heat capacity measurements, performed down to 0.4 K, revealed that Yb3Pt23Si11 is a moderately enhanced paramagnetic compound with fairly unstable 4f electronic shell.

Five novel cerium-based ternaries Ce2Rh3.1Si0.9 ,C e 4Rh12Si, Ce8Rh21.9Si3.1, CeRh1.82Si0.18 and CeRh3Si0.125 were studied by means of magnetic susceptibility and electrical resistivity measurements. All these phases were found to be Pauli paramagnets with metallic type of electrical conductivity.

We have studied chemical interaction of the intermetallic compound NdRh3 with hydrogen at pressures of up to 0.2 GPa. The structural changes in the intermetallic matrix in different stages of the hydrogenation process have been followed using synchrotron X-ray diffraction. The results demonstrate that hydrogen absorption leads to an irreversible change in lattice symmetry from hexagonal to cubic.

Two series of intermetallic alloys, RT2Si and RTSi2, have been synthesized from stoichiometric compositions. The crystal structures of EuPt1+xSi2−x (CeNiSi2-type), CeIr2Si (new structure type), YbPd2Si and YbPt2Si (both YPd2Si-type) have been elucidated from X-ray single crystal CCD data, which were confirmed by XPD experiments. The crystal structures of LaRh2Si and LaIr2Si (CeIr2Si-type), {La,Ce,Pr,Nd}AgSi2 (all TbFeSi2-type), and EuPt2Si (inverse CeNiSi2-type) were characterized by XPD data. RT2Si/RTSi2 compounds were neither detected in as-cast alloys Sc25Pt50Si25, Eu25Os25Si50 and Eu25Rh25Si50 nor after annealing at 900 °C. Instead, X-ray single crystal data prompted Eu2Os3Si5 (Sc2Fe3Si5-type) and EuRh2+xSi2−x (x=0.04, ThCr2Si2-type) as well as a new structure type for Sc2Pt3Si2 (own type).

Phase relations in the ternary system Ce–Pd–Si have been established for the isothermal section at 8001C based on X-ray powder diffraction and EMPA techniques on about 130 alloys, which were prepared by arc-melting under argon or powder reaction sintering. Eighteen ternary compounds have been observed to participate in the phase equilibria at 8001C. Atom order was determined by direct methods from X-ray single-crystal counter data for the crystal structures of t8—Ce3Pd4Si4 (U3Ni4Si4type, Immm; a ¼ 0.41618(1), b ¼ 0.42640(1), c ¼ 2.45744(7) nm), t16—Ce2Pd14Si (own structure type, P4/nmm; a ¼ 0.88832(2), c ¼ 0.69600(2) nm) and also for t18—CePd1� xSix (x ¼ 0.07; FeB-type, Pnma; a ¼ 0.74422(5), b ¼ 0.45548(3), c ¼ 0.58569(4) nm). Rietveld refinements established the atom arrangement in the structures of t5—Ce3PdSi3 (Ba3Al2Ge2-type, Immm; a ¼ 0.41207(1), b ¼ 0.43026(1), c ¼ 1.84069(4) nm) and t13—Ce3� xPd20+xSi6 (0rxr1, Co 20Al3B6-type, Fm3 ¯ m; a ¼ 1.21527(2) nm). The ternary compound Ce2Pd3Si3 (structure-type Ce2Rh1.35Ge4.65, Pmmn; a ¼ 0.42040(1), b ¼ 0.42247(1), c ¼ 1.72444(3) nm) was detected as a high-temperature compound, however, does not participate in the equilibria at 8001C. Phase equilibria in Ce–Pd–Si are characterized by the absence of cerium solubility in palladium silicides. Mutual solubility among cerium silicides and cerium–palladium compounds are significant whereby random substitution of the almost equally sized atom species palladium and silicon is reflected in extended homogeneous regions at constant Cecontent such as for t2—Ce(PdxSi1� x)2 (AlB2-derivative type), t6—Ce(PdxSi1� x)2 (ThSi2-type) and t7—CePd2� xSi2+x. The crystal structures of compounds t4—Ce� 8Pd� 46Si� 46, t12—Ce� 29Pd� 49Si� 22, t15—Ce� 22Pd� 67Si� 11, t17—Ce� 5Pd� 77Si� 18 and t18—CePd1� xSix (x� 0.1) are still unknown.

The crystal structures of ternary compounds RPt3−xSi1−y(R=Y, Tb, Dy, Ho, Er, Tm, Yb) have been elucidated from X-ray single crystal CCD data. All compounds are isotypic and crystallize in the tetragonal space group P4/mbm. The general formula RPt3−xSi1−y arises from defects: x≈0.20, y≈0.14. The crystal structure of RPt3−xSi1−y can be considered as a packing of four types of building blocks which derive from the CePt3B-type unit cell by various degrees of distortion and Pt, Si-defects.

Among the many documents released one way or another during the early 1990s, there are two that open the window into the perception of samizdat by the top Soviet authorities. The first of them was signed by Yuri Andropov, then the head of the KGB, in the last days of December 1970. It was a memo addressed to the Central Committee of the Communist Party of the Soviet Union reporting on the status of samizdat in the country and suggesting some practical steps that would diminish the spread and impact of uncontrolled publications in the USSR. The second document, dated in the last days of April 1971, was compiled in response to Andropov's memo. It was a statement by the Central Committee regarding samizdat. The Central Committee document for the most part accepted the KGB recommendations but took a broader view of the samizdat phenomenon and for the first time offered a definition of samizdat, which was missing in the KGB memo. The differences between the two documents allow a glimpse of their respective institutional thinking about samizdat. Andropov's document implied that the samizdat phenomenon was so widespread that the repressive apparatus could not cope with it in the framework of its current charter. In response, the Central Committee document expanded the responsibility of the party apparatus with respect to suppression of uncontrolled publications.

Phase relations in the ternary system Ce–Pt–Si have been established for the isothermal section at 800 °C based on X-ray powder diffraction, metallography, scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) techniques on about 120 alloys, which were prepared by various methods employing arc-melting under argon or powder reaction sintering. Nineteen ternary compounds were observed. Atom order in the crystal structures of τ18-Ce5(Pt,Si)4 (Pnma; a=0.77223(3) nm, b=1.53279(8) nm c=0.80054(5) nm), τ3-Ce2Pt7Si4 (Pnma; a=1.96335(8) nm, b=0.40361(4) nm, c=1.12240(6) nm) and τ10-CePtSi2 (Cmcm; a=0.42943(2) nm, b=1.67357(5) nm, c=0.42372(2) nm) was determined by direct methods from X-ray single-crystal CCD data and found to be isotypic with the Sm5Ge4-type, the Ce2Pt7Ge4-type and the CeNiSi2-type, respectively. Rietveld refinements established the atom arrangement in the structures of Pt3Si (Pt3Ge-type, C2/m, a=0.7724(2) nm, b=0.7767(2) nm, c=0.5390(2) nm, β=133.86(2)°), τ16-Ce3Pt5Si (Ce3Pd5Si-type, Imma, a=0.74025(8) nm, b=1.2951(2) nm, c=0.7508(1) nm) and τ17-Ce3PtSi3 (Ba3Al2Ge2-type, Immm, a=0.41065(5) nm, b=0.43221(5) nm, c=1.8375(3) nm). Phase equilibria in Ce–Pt–Si are characterised by the absence of cerium solubility in platinum silicides. Cerium silicides and cerium platinides, however, dissolve significant amounts of the third component, whereby random substitution of the almost equally sized atom species platinum and silicon is reflected in extended homogeneous regions at constant Ce content such as for τ13-Ce(PtxSi1−x)2, τ6-Ce2Pt3+xSi5−x or τ7-CePt2−xSi2+x.

Ternary intermetallic CeRu 0.88 In 2 was synthesized by arc-melting from elemental Ce, Ru, and In under an argon atmosphere. The crystal structure of CeRu 0.88 In 2 was determined from single-crystal X-ray diffraction data: a = 4.5449(11) A, b = 10.014(2) A and c = 7.6854(10) A; space group Cmcm , Z = 4, MgCuAl 2 type. The structure is formed of three-dimensional framework of [Ru 0.88 In 2 ], in the infinite pentagonal channels of which Ce atoms are disposed. Similar to the other known ternary compounds of the Ce–Ru–In system, CeRu 0.88 In 2 exhibits unusually short Ce–Ru contact equal to 2.530(4) A, which in addition is the shortest one in the raw of LTIn 2 compounds with MgCuAl 2 structure type (L = La, Ce, Pr, Nd, Sm, Eu, Gd, Yb; T = Rh, Pd, Au).

The ternary intermetallic Ce 16 Ru 8 In 37 was synthesized by arc-melting from elemental Ce, Ru, and In under an argon atmosphere. The crystal structure of Ce 16 Ru 8 In 37 was determined from the single-crystal X-ray diffraction data: a = 4.7451(1) A, b = 9.3518(2) A, c = 32.6162(7) A; space group Immm , Z = 1. The architecture of the crystal structure of Ce 16 Ru 8 In 37 is based on CeIn 3 units with cubic Cu 3 Au-type and can be presented as consisting of two different slabs: CeIn 3 -like slab of composition Ce 4 In 14.5 and a slab of composition Ce 4 Ru 4 In 4 .

Cerium ruthenium indides, Ce2Ru2In3 and Ce3Ru2In2, were synthesized from the pure elements by arc-melting. Both structures present a site exchange variant of a new structure type with different occupation of one crystallographic site: space group Pnma, Z = 4, oP28, with cell parameters a = 17.7054(4) A, b = 4.7144(1) A, c = 7.4072(1) A for Ce2Ru2In3, and a = 17.394(2) A, b = 4.9073(6) A, c = 7.669(1) A for Ce3Ru2In2 at room temperature. In the structures there are eight extremely short Ce–Ru contacts per unit cell: Ce1–Ru1 = 2.3225(8) A, Ce1–Ru2 = 2.3681(8) A in Ce2Ru2In3, and Ce1–Ru1 = 2.2345(9) A, Ce3–Ru2 = 2.2811(9) A in Ce3Ru2In2. Such contacts cause considerable distortion of coordination polyhedra of all atoms and reduce cell parameter a by 1 A when compared to the parent NdRh2Sn4 structure.

The dynamic magnetic response of the intermediate-valence compound EuCu2Si2 has been studied using inelastic neutron scattering. At low temperatures, strong renormalization of the 7F0 → 7F1 spin-orbit transition energy is detected; it is likely to be related to partial delocalization of the f electrons of Eu. An increase in the temperature increases the valence instability of europium and results in further changes in the magnetic excitation spectrum parameters and the appearance of an intense quasi-elastic component.

Polycrystalline Ce2Ru2Al is prepared by arc melting of the elements and subsequent annealing (evacuated quartz ampoules, 823 K, 30 d).

CePd2Al2 (I), CePd3Al3 (II), CePd3.04Al2.96, CePd4Al4 (III), and CePd4.06Al3.94 are prepared by arc melting of the elements followed by annealing (evacuated quartz tubes, 1070 K, ≥ 30 d).

The crystal structure of a new low-temperature modification of CePdAl was determined from single-crystal x-ray data: CePdAl-type; space group Pmmn (No. 59), Z = 14, oP42, a = 0.426 07 nm, b = 2.887 58 nm, c = 0.721 90 nm; RF = 0.048. Physical properties of orthorhombic CePdAl are governed by a mutual balance of the RKKY interaction, the Kondo effect and crystalline electric field splitting, resulting in antiferromagnetic ordering below ≈2.5 K. Electronic transport is reminiscent of a textbook-like Kondo lattice, which comes along with a significant negative magnetoresistance of more than 50% at low temperatures. Although geometrical frustration is absent when compared to the hexagonal modification of CePdAl, the ordering temperature TN is even smaller. A possible cause is enhanced Kondo interactions.

The ternary intermetallic compounds Ce 0.67 Pt 2 Al 5 ( I ) and Ce 1.33 Pt 3 Al 8 ( II ) were synthesized in the Ce–Pt–Al system by the reaction of elemental Ce, Pt, and Al in an arc furnace under an argon atmosphere. The crystal structures of I and II were determined from single-crystal X-ray diffraction data. The crystals are characterized by the following unit cell parameters: a = 4.3105(18) A, c = 16.494(5) A, space group P 6 3 / mmc , Z = 2 ( I ) and a = 4.361(2) A, c = 39.00(2) A, space group R 3 ¯ m , Z = 6 ( II ). Both compounds have structures with different packing of layers.

CePt 3 Si is a novel ternary compound exhibiting antiferromagnetic order at T N ≈ 2.2 K and superconductivity (SC) at T c ≈ 0.75 K . Large values of H c 2 ′ ≈ - 8.5 T / K and H c 2 ( 0 ) ≈ 5 T indicate Cooper pairs formed out of heavy quasiparticles. The mass enhancement originates from Kondo interaction with a characteristic temperature T K ≈ 8 K . NMR and μ SR measurements evidence coexistence of SC and long-range magnetic order on a microscopic scale. Moreover, CePt 3 Si is the first heavy fermion SC without an inversion symmetry. This gives rise to a novel type of NMR relaxation rate 1 / T 1 which is very unique and never reported before for other heavy fermion superconductors. Studies of Si/Ge substitution allow us to establish a phase diagram.

Novel representatives REPt3Si (RE = La, Pr, Nd, Sm and Gd) of the CePt3B type have been synthesized and characterized by means of Rietveld x-ray powder diffraction. Measurements of the magnetic susceptibility, isothermal magnetization, temperature dependent specific heat as well as temperature and field dependent resistivity were employed to derive basic information on the low temperature behaviour. Long range antiferromagnetic order from 2.2 K (CePt3Si) to 15.1 K (GdPt3Si) was observed. PrPt3Si, however, is non-magnetic, at least down to 400 mK, as a consequence of crystalline electric field splitting of the non-Kramers ion Pr3+ in tetragonal symmetry. Whilst the ordering temperature of SmPt3Si appears to be almost unaffected in external fields up to 12 T, magnetic order in GdPt3Si, although twice as high as for the Sm homologue, is easily suppressed by external magnetic fields due to the absence of anisotropy.

The electronic and magnetic properties of the ternary cerium compounds Ce 2 PdGe 6 and Ce 2 PtGe 6 are reported within the context of measurements of electrical resistivity, magnetoresistivity, and magnetic susceptibility. Ce 2 PdGe 6 orders magnetically at T N = 11.5 K , and Ce 2 PtGe 6 at T N = 9.9 K . In the ordered region, the magnetization as well as the magnetoresistance reveal anomalous behaviour for both compounds, which are ascribed to metamagnetic transitions into a field-induced ferromagnetic state.

The interaction of the components in the Ce–Pt–Si system at 600 °C was investigated over the whole concentration range by X-ray powder and single crystal diffraction, DTA, and electron probe X-ray analysis. There are nine ternary compounds in the Ce–Pt–Si system. The crystal structures of eight of them were determined.

The crystal and magnetic structures of U(Pd 1− x M x ) 2 Ge 2 compounds with M=Fe, Co, Ru are studied by neutron powder diffraction and μSR. The effects of M doping and external applied pressure on the crystal and magnetic structures are compared. We find that even at small M-doping level the magnetic structure drastically changes, while the values of the lattice parameters and interatomic distances change only slightly. In contrast, a high external pressure modifies the crystal structure more significantly, while the magnetic structure remains the same. These observations allow us to conclude that the drastic changes of magnetic structure of U(Pd 1− x M x ) 2 Ge 2 compounds with increased M doping could result from modifications of the RKKY indirect exchange interactions owing to a variation of conduction-electron number per U atom, rather than from lattice contraction.

The crystal structure of the U(Pd1−xFex)2Ge2 compounds with Fe content x = 0– 0.03 and the crystal and magnetic structure of U(Pd0.98Fe0.02)2Ge2 at high external pressures up to 4.5 GPa were studied by means of powder neutron diffraction in the temperature range 1.5–300 K. With increasing Fe content the values of the lattice parameters and interatomic distances change only slightly, but it is known from previous experiments that the magnetic structure changes drastically for x ≥ 0.015. In contrast to this, high external pressure modifies the crystal structure more significantly while the magnetic structure remains unchanged. The results obtained allow one to infer that drastic changes in the magnetic structure of the U(Pd1−xFex)2Ge2 compounds with increasing Fe content are a consequence of modification of the RKKY-type (RKKY standing for Ruderman, Kittel, Kasuya and Yosida) indirect exchange interaction due to the variation of the number of conduction electrons per U atom rather than a result of lattice contraction.

The magnetic ordering of the ternary intermetallic compound U(Pd1-xFex)2Ge2 (x = 0.01, 0.02) was studied by µSR in the temperature range T = 15-300 K. The low temperature state changes from the modulated longitudinal spin density wave LSDW (x = 0.01) with a propagation vector k = [0 0 3/4] (TN = 140 K) to a simple antiferromagnetic structure AF (x = 0.02) with k = [0 0 1] (TN = 140 K). In the AF phase (sample with x = 0.02) the uranium magnetic moment shows a monotonic temperature dependence. In the LSDW phase with k = [0 0 3/4] (sample with x = 0.01) the magnetic moments of uranium atoms located in two magnetically nonequivalent positions (0 0 0) and (0 0 1) have different temperature dependences. One moment assumes a maximum at Tm1 = 50 K, while the other one does not display any peculiarities. The results are discussed within a model of the superposition of a square and sine modulation and are compared with neutron diffraction data. The observed peculiar temperature behaviour of the moments is connected with the temperature variation of the initial phase of the LSDW modulation by Δ = 0.2 rad.