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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.

We report lSR studies on a Ce 3 Pd 20 Si 6 polycrystalline sample. Zero-"eld measurements were undertaken to gain information on the magnetic ordering at low temperatures. Below 0.4 K the increase of the muon-spin depolarization rate re#ects the development of a quasi-static ordering of magnetic moments of electronic origin probably randomly oriented. In transverse-"eld studies a clear frequency shift was observed. This fact may be ascribed to the increase of the total-magnetic moment of the superparamagnetic cube containing 8 Ce2 atoms and their ferromagnetic ordering with decreasing temperature. ( 2000 Elsevier Science B.V. All rights reserved.

The low-temperature state of U ( Pd 1−x Fe x ) 2 Ge 2 (x=0.01, 0.02) is transformed from simple anti-ferromagnetism AF (x=0.02) with a propagation vector k =[0 0 1] to the modulated longitudinal spin density wave LSDW (x=0.01) with k =[0 0 3 4 ] . ZF-μSR showed that in the sample with x=0.01 the magnetic moments of uranium atoms in two magnetically nonequivalent positions (0 0 0) and (0 0 1) have different temperature dependencies. The results are discussed in the model of a superposition of square and sine shape of modulation in comparison with neutron diffraction data. It is shown, that the observed temperature behavior of moments can be connected with the temperature variation of the initial phase of LSDW modulation.

The neutron diffraction and magnetic susceptibility studies have shown that the magnetic structure of UPd 2 Ge 2 changes dramatically even under very low iron doping. Though the general magnetic structure of pure UPd 2 Ge 2 and of 1%Fe-doped samples is the same, the temperature intervals of existence of different magnetic phases are different. The values of transition temperatures, where (i) the `square’ modulated longitudinal spin-density wave (LSDW) structure with the propagation vector k =(0; 0; k z = 3 4 ) starts to transform into the sinusoidal modulated LSDW structure and (ii) the commensurate phase transforms into incommensurate one, shift under the 1%Fe doping to the higher temperatures (from 50 to 65 K and from 80 to 90 K, respectively). In the pure and 1%Fe-doped UPd 2 Ge 2 , the magnetic transition from the commensurate to incommensurate phase is accompanied by the drastic decrease of the propagation vector k z . In the 2%Fe-doped sample, besides the Neel point of T N =135 K, we have found two additional characteristic temperatures of 65 and 93 K. Below 65 K, the material has a simple antiferromagnetic (AF) structure with the propagation vector k =(0; 0; 1) and, at 65 K T T N , the magnetic structure is LSDW with sinusoidal modulation. Over almost the total region 65 K T T N , the LSDW magnetic structure is incommensurate. Only at about 93 K, the propagation vector passes the commensurate value of 3 4 , whereas k z > 3 4 at 65 T k z 3 4 at 93 K T T N . We have found that the magnetic susceptibility and the uranium magnetic moment are sensitive to the k z > 3 4 ⇒k z 3 4 transition. With increasing iron concentration to x ⩾0.15, the simple AF structure with k =(0; 0; 1) develops over all temperature region up to the Neel point. Below T N , the uranium magnetic moments are always parallel to the tetragonal c -axis.

Phase equilibria in the Sm–{Pd,Pt}–{Si,Ge} systems were studied at 870 K, and intermetallic compounds containing 20 at.% Sm were characterized by physical–chemical analysis methods.

The crystal structure of the new intermetallide Ce 3 Pd 14 Ge 5 was investigated by X-ray monocrystal diffraction method. It is found that the elementary cell belongs to space group Pnma, Z =4, a =0.9033(2) nm, b =0.9082(2) nm, c =1.8142(2) nm.

A novel ternary compound has been found at the 1:2:1 position among the Yb–Pd–Si phases, where YbPd 2 Si crystallises in the ordered Fe 3 C -structure. YbPd 2 Si is characterised by Kondo lattice features at higher temperatures and, presumably, antiferromagnetism at 2.1 K. A quasi-quartet crystal field ground state governs the physics at low temperature.

CePt 2 Si crystallizes in the inverse CeNiSi 2 -type structure. Magnetic properties are dominated by a mutual interaction of the RKKY interaction, the Kondo effect and crystalline electric field splitting, resulting in long range magnetic order below about 7 K . A slightly enhanced Sommerfeld value γ = 42 mJ / mol K 2 and a distinct temperature dependence of the electrical resistivity refers to Kondo interaction in presence of strong crystalline electric field splitting.

Physico-chemical analysis techniques, including X-ray phase analysis and differential thermal analysis were employed for the characterisation of compounds including their melting temperature. The melting temperature of 23 RT2X2 compounds belonging to the CeGa2Al2 structure has been measured. The melting temperature of 19 RTX2 compounds belonging to the CeNiSi2 structure has been measured (LaCoSi2, LaNiSi2, CeFeSi2, CeCoSi2, CeNiSi2, SmCoSi2, SmNiSi2, ErCoSi2, ErNiSi2, TmCoSi2, TmNiSi2, LaCoGe2, LaNiGe2, CeFeGe2, CeCoGe2, CeNiGe2, SmFeGe2, SmCoGe2, SmNiGe2). It is established, that the new ternary compound SmCoSi2 belongs to the CeNiSi2 structure type (group Cmcm, a=0.4088(1) nm, b=1.6320(3) nm, c=0.4008(1) nm).

Copyright (c) 1997 Elsevier Science S.A. All rights reserved. A novel ternary compound Ce 3 Pt 23 Ge 11 crystallises in a new structure type with space group F 3m and a=1.71833(9) nm. Here we present the results of magnetic, electrical and specific heat measurements, obtained on the single crystal and polycrystalline samples. This compound is a metal with normal Ce 3+ magnetic behaviour. Although the specific heat at low temperatures rises rapidly to a large value of 2.5 J/Ce-mol K at 0.38 K, we have not detected any phase transition down to this temperature. Only in the temperature range 0.1-1 K a small decrease in the resistivity value can be detected with an inflection point at approximately 0.3 K.

Measurements of temperature and field dependent bulk properties have been carried out on ${{\mathrm{Ce},\mathrm{La}}}_{3}{\mathrm{Pd}}_{4}{\mathrm{Si}}_{4}$. Rietveld refinements of x-ray powder intensity data confirm the orthorhombic ${\mathrm{U}}_{3}{\mathrm{Ni}}_{4}{\mathrm{Si}}_{4}$-type structure for both compounds. While ${\mathrm{La}}_{3}{\mathrm{Pd}}_{3}{\mathrm{Si}}_{4}$ exhibits superconductivity below 2 K together with some indications of a two gap scenario, the former can be characterized as a Kondo lattice system in presence of crystalline electric field splitting. Due to the closeness of a quantum critical point, distinct non-Fermi-liquid features dominate the low temperature physics of ${\mathrm{Ce}}_{3}{\mathrm{Pd}}_{4}{\mathrm{Si}}_{4}$.

The title compound is unintentionally obtained by arc melting of the elements in a ratio pertaining to YbPtSi2 with 3 wt.% excess of Yb due to its high volatility.The crystal structure of the novel intermetallic is determined by single crystal XRD (space group P21/m, Z = 2) and found to be a disordered variant of the Y3Pt4Ge6 type characterized by the intergrowth of slabs cut from the ThCr2Si2 and YIrGe2 types of structures.

Metamagnetic transitions in CePd5Ge3 were investigated by means of low-temperature magnetization, magnetic susceptibility, electrical resistivity and magnetoresistivity measurements. In transverse magnetic fields applied in a direction close to the b-axis the antiferromagnetic structure of the compound undergoes two successive transitions, first to a spin-flop phase and then to a paramagnetic phase with field-induced ferromagnetic-like alignment of the Ce magnetic moments. In contrast, a single anomaly occurs in the magnetic field dependences of the resistivity in a transverse magnetic field applied close to the c-axis, which reflects a direct transition from antiferromagnetic to paramagnetic state. Such behavior is in agreement with theoretical descriptions of metamagnetic transitions in uniaxial antiferromagnets. The experimental magnetic and electrical transport data indicate that the b-axis is the easy axis of magnetization in CePd5Ge3.

The crystal structure of the new ternary silicide CePt 3 Si [space group P 4 mm , a =4.072(1) A, c =5.442(2) A, Z =1, V =90.25(5) A 3 , R =0.0437 for 153 structure factors] was determined from single-crystal X-ray diffraction. The compound belongs to the CePt 3 B structure type of intermetallic compounds.

The crystal structure of the compound CeRh 2 Si was studied by X-ray single crystal diffraction methods and refined to R F =0.038: space group Cmcm , a =4.0413(9) A, b =17.730(3) A, c =4.0675(9) A, V =291.45(10) A 3 , Z =4. The structure belongs to a structure type that can be considered as a site exchange variant of the known CeNiSi 2 structure type (CeSiRh 2 ) with slightly different axial ratios.

The crystal structure of the intermetallic compound Ce 3 Ru 4 Al 12 has been studied. The experiment was carried out using the X-ray single crystal diffraction technique. It was established that the structure belongs to the Gd 3 Ru 4 Al 12 structure type, which is related to the EuMg 5.2 type. Ce 3 Ru 4 Al 12 has the space group P6 3 /mmc, a = 8.8652(10) A, c = 9.5700(2) A, V = 651.4(2) A 3 , and Z = 2.

We report the inelastic neutron scattering study of spin dynamics in EuCu(2)(Si(x)Ge(1-x))(2) (x = 1, 0.9, 0.75, 0.6), performed in a wide temperature range. At x = 1 the magnetic excitation spectrum was found to be represented by the double-peak structure well below the energy range of the Eu(3+) spin-orbit (SO) excitation (7)F(0)→(7)F(1), so that at least the high-energy spectral component can be assigned to the renormalized SO transition. Change of the Eu valence towards 2 + with increased temperature and/or Ge concentration results in further renormalization (lowering the energy) and gradual suppression of both inelastic peaks in the spectrum, along with developing sizeable quasielastic signal. The origin of the spectral structure and its evolution is discussed in terms of excitonic model for the mixed valence state.

The new title compound is prepared by arc melting of the elements and its crystal structure is determined by powder XRD.

The crystal structure of the new ternary compound, Ce 3 Pt 23 Si 11 , was determined by X-ray analysis of a single crystal (Enraf-Nonius CAD-4 diffractometer, Mo Kα radiation, 585 independent reflections, R =0.0487). The Ce atoms have only one crystallographic position with a very rare tetragonal prism coordination polyhedron.

The title compound is prepared by arc melting of the elements and characterized by powder XRD and magnetic, electrical resistivity, and heat capacity measurements.

The new compounds CeRh1.82Si0.18, CeRh3Si0.125, Ce2Rh3.1Si0.9, Ce4Rh12Si, and Ce8Rh21.9Si3.1 are prepared by arc melting of the elements followed by annealing at 950 °C for two weeks.

The crystal structure of the compound Ce3Pt23Ge11 has been determined by X-ray analysis of a single crystal (Enraf-Nonius CAD-4 autodiffractometer, Mo Kα radiation, 276 independent reflections, R-factor 0.0735 in isotropic approximation). This structure has been found to belong to a new structural type: space group F 4 3m, a = 17.1833(9) A , Z = 8 . The coordination polyhedra of the cerium atoms are compressed cubes, those of platinum have eight or 10 apexes and those of germanium are either trigonal prisms with an additional atom or cubes. The magnetic properties of Ce3Pt23Ge11 at low temperatures (4–100 K) were investigated. A diffuse magnetic phase transition at around 10 K was detected.

The crystal structure of the compound Ce 7 Pd 4 Ge 2 has been determined by X-ray analysis of a single crystal (Dartch autodiffractometer, Mo Kα radiation, 1116 independent reflections, reliability factor R = 0.0491 in the anisotropic approximation). This structure has been found to belong to a new structural type: space group P2 1 /n, a = 9.315(2) A , b = 12.277(7) A , c = 12.698(3) A , β = 114.31(2)° , Z = 4. The coordination polyhedra of the cerium atoms have 15 and 17 apexes, those of palladium are trigonal prisms with three additional atoms and a tetragonal antiprism with one additional atom, and those of germanium are trigonal prisms with three additional atoms.

The crystal structure of the new intermetallic compound Ce 4 Pd 29 Si 14 , was determined by X-ray single-crystal diffraction method revealing space group Fm3m with a =1.8010(2) nm and Z =4.

The crystal structure of the new compound Ce 3 Pd 5 Si was investigated by X-ray single crystal diffraction method. The compound crystallizes in a new structure type, space group Imma Z =4, a =1.3027(4) nm, b =0.7377(4) nm, c =0.7580(4) nm.

The interaction of the components in the Er–Co–Pd system at 600°C was investigated over the composition range 0–50 at% of erbium by X-ray powder, metallography, electron probe microanalysis (EPMA), DTA and SEM. The isothermal section at 600°C was determined based on these results.

The intermetallic compound CePd5Ge3 has been studied by means of magnetisation, magnetic susceptibility, electrical resistivity and specific heat measurements. The results indicate the presence of stable Ce3+ ions, but nevertheless the compound does not order magnetically down to 2 K. However, some hints on magnetic ordering below 2 K may be deduced from anomalous low temperature behaviour of the magnetisation, resistivity and specific heat. The properties of CePd5Ge3 are discussed in terms of possible Kondo interactions.

The crystal structure of the compound Ce 7 Pd 4 Ge 2 has been determined by X-ray analysis of a single crystal (Dartch autodiffractometer, Mo Kα radiation, 1116 independent reflections, reliability factor R = 0.0491 in the anisotropic approximation). This structure has been found to belong to a new structural type: space group P2 1 /n, a = 9.315(2) A , b = 12.277(7) A , c = 12.698(3) A , β = 114.31(2)° , Z = 4. The coordination polyhedra of the cerium atoms have 15 and 17 apexes, those of palladium are trigonal prisms with three additional atoms and a tetragonal antiprism with one additional atom, and those of germanium are trigonal prisms with three additional atoms.

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 have been established in the ternary system Ce-Rh-Si for the isothermal section at 800 deg. C based on X-ray powder diffraction and EPMA on about 80 alloys, which were prepared by arc melting under argon or by powder reaction sintering. From the 25 ternary compounds observed at 800 deg. C 13 phases have been reported earlier. Based on XPD Rietveld refinements the crystal structures for 9 new ternary phases were assigned to known structure types. Structural chemistry of these compounds follows the characteristics already outlined for their prototype structures: tau{sub 7}-Ce{sub 3}RhSi{sub 3}, (Ba{sub 3}Al{sub 2}Ge{sub 2}-type), tau{sub 8}-Ce{sub 2}Rh{sub 3-x}Si{sub 3+x} (Ce{sub 2}Rh{sub 1.35}Ge{sub 4.65}-type), tau{sub 10}-Ce{sub 3}Rh{sub 4-x}Si{sub 4+x} (U{sub 3}Ni{sub 4}Si{sub 4}-type), tau{sub 11}-CeRh{sub 6}Si{sub 4} (LiCo{sub 6}P{sub 4}-type), tau{sub 13}-Ce{sub 6}Rh{sub 30}Si{sub 19.3} (U{sub 6}Co{sub 30}Si{sub 19}-type), tau{sub 18}-Ce{sub 4}Rh{sub 4}Si{sub 3} (Sm{sub 4}Pd{sub 4}Si{sub 3}-type), tau{sub 21}-CeRh{sub 2}Si (CeIr{sub 2}Si-type), tau{sub 22}-Ce{sub 2}Rh{sub 3+x}Si{sub 1-x} (Y{sub 2}Rh{sub 3}Ge-type) and tau{sub 24}-Ce{sub 8}(Rh{sub 1-x}Si{sub x}){sub 24}Si (Ce{sub 8}Pd{sub 24}Sb-type). For tau{sub 25}-Ce{sub 4}(Rh{sub 1-x}Si{sub x}){sub 12}Si a novel bcc structure was proposed from Rietveld analysis. Detailed crystal structure data were derived for tau{sub 3}-CeRhSi{sub 2} (CeNiSi{sub 2}-type) and tau{sub 6}-Ce{sub 2}Rh{sub 3}Si{sub 5} (U{submore » 2}Co{sub 3}Si{sub 5}-type) by X-ray single crystal experiments, confirming the structure types. The crystal structures of tau{sub 4}-Ce{sub 22}Rh{sub 22}Si{sub 56}, tau{sub 5}-Ce{sub 20}Rh{sub 27}Si{sub 53} and tau{sub 23}-Ce{sub 33.3}Rh{sub 58.2-55.2}Si{sub 8.5-11.5} are unknown. High temperature compounds with compositions Ce{sub 10}Rh{sub 51}Si{sub 33} (U{sub 10}Co{sub 51}Si{sub 33}-type) and CeRhSi (LaIrSi-type) have been observed in as-cast alloys but these phases do not participate in the phase equilibria at 800 deg. C. - Graphical abstract: Phase relations in the ternary system Ce-Rh-Si have been established for the isothermal section at 800 deg. C based on X-ray powder and single-crystal diffraction, metallography, SEM and EMPA techniques on about 80 alloys. 25 ternary compounds were observed.« less

Copyright (c) 1997 Elsevier Science S.A. All rights reserved. A novel ternary compound Ce 3 Pt 23 Ge 11 crystallises in a new structure type with space group F 3m and a=1.71833(9) nm. Here we present the results of magnetic, electrical and specific heat measurements, obtained on the single crystal and polycrystalline samples. This compound is a metal with normal Ce 3+ magnetic behaviour. Although the specific heat at low temperatures rises rapidly to a large value of 2.5 J/Ce-mol K at 0.38 K, we have not detected any phase transition down to this temperature. Only in the temperature range 0.1-1 K a small decrease in the resistivity value can be detected with an inflection point at approximately 0.3 K.

The crystal structure of the new intermetallide Ce 3 Pd 14 Ge 5 was investigated by X-ray monocrystal diffraction method. It is found that the elementary cell belongs to space group Pnma, Z =4, a =0.9033(2) nm, b =0.9082(2) nm, c =1.8142(2) nm.

The isothermal section at 600°C of the Yb–Pt–Ge phase diagram was investigated using metallography, X-ray powder diffraction and electron probe microanalysis. Only one binary compound, Yb 3 Ge 5 , was found in the Yb–Ge system. In the ternary Yb–Pt–Ge system the formation of the three phases, Yb 2 PtGe 6 , YbPtGe 2 , and YbPtGe was observed. The crystal structures of these compounds were determined.

The crystal structure of the new intermetallic compound Ce 4 Pd 29 Si 14 , was determined by X-ray single-crystal diffraction method revealing space group Fm3m with a =1.8010(2) nm and Z =4.

The cerium effective valence was investigated by means of CeL 3 -XANES spectroscopy in some intermediate valence Ce-based systems with different magnetic ordering mechanisms: CeNi doped with Nd, Pr and Gd in the temperature range 5-300 K, and Ce 2 Fe 17-x Mn x intermetallics. The dependences obtained are considered within the frames of generally accepted mechanisms of rare-earth ions intermediate valence states. Possible correlations between the cerium effective valence and the magnetic properties of compounds are also noted.

The crystal structure of the compound Ce 3 Pt 4 Ge 6 has been determined by X-ray analysis of a single crystal (Enraf-Nonius CAD-4 autodiffractometer, Mo Kα radiation, 208 independent reflections, R = 0.033 in the anisotropic approximation). This structure has been found to belong to a new structural type: space group Bmmb , a = 4.419(1) A , b = 4.422(1) A , c = 26.222(5) A , Z = 2 . The coordination polyhedra of cerium atoms have 19 and 21 apexes; those of platinum are tetragonal antiprisms with two additional atoms and trigonal prisms with four additional atoms; those of germanium are trigonal prisms with three additional atoms and distorted cubo-octahedra.

The isothermal section at 600°C of the Yb–Pt–Ge phase diagram was investigated using metallography, X-ray powder diffraction and electron probe microanalysis. Only one binary compound, Yb 3 Ge 5 , was found in the Yb–Ge system. In the ternary Yb–Pt–Ge system the formation of the three phases, Yb 2 PtGe 6 , YbPtGe 2 , and YbPtGe was observed. The crystal structures of these compounds were determined.

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.

H. Kaldarar,1 E. Royanian,1 H. Michor,1 G. Hilscher,1 E. Bauer,1 A. Gribanov,2,3 D. Shtepa,2 P. Rogl,3 A. Grytsiv,3 Y. Seropegin,2 and S. Nesterenko2 1Institute of Solid State Physics, Vienna University of Technology, Wien A-1040, Austria 2Department of Chemistry, Moscow State University, Leninskie Gory, GSP-1, Moscow 119991, Russia 3Institute of Physical Chemistry, University of Vienna, Wahringerstrasse 42, Wien A-1090, Austria Received 13 November 2008; published 7 May 2009

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 crystal structures of the compounds CeRuAl and CeRhAl were studied by single crystal X-ray diffraction. Both compounds crystallize in the orthorhombic LaNiAl type with space group Pnma (No. 62) and are related to the structure types of hexagonal ZrNiAl and orthorhombic TiNiSi. Parameters for CeRuAl and CeRhAl are: a = 7.2057(2) A, b = 4.0589(1) A, c = 15.8728(5) A; R F = 0.023; a = 7.107(2) A, b = 4.2237(10) A, c = 15.965(3) A; R F = 0.032, respectively.

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 .

The crystal structure of the new intermetallic compound CePd 5 Ge 3 belongs to the YNi 5 Si 3 structure type, space group Pnma, Z =4, a =2.024(1) nm, b =0.4122(1) nm, c =0.7244(3) nm.

The ternary intermetallic compound CeRu 3− x Al 10+ x ( x = 0.17) crystallizes in the orthorhombic system, space group Imma , a = 4.2213(1) A, b = 12.5014(3) A, c = 17.6689(4) A, Z = 4. It is closely related to NdCo 3 Ga 9 and can be regarded as a substructure of U 2 Co 6 Al 19 . Trigonal prismatic and cuboctahedral coordination is typical for Al and Ru atoms, the coordination polyhedron of the Ce atom is a pentagonal prism with five additional atoms. The structure can be described as a 3D network of aluminium and ruthenium atoms, forming distorted pentagonal channels along [1 0 0], where the cerium atoms are located.

The crystal structures of the compounds Dy18Pt50+xSi16−x (x = 0.28) (I) and Y18Pt50+xSi16−x (x = 0.56) (II) have been investigated by means of single crystal techniques (Nonius KappaCCD diffractometer, ω- and φ-scans, Mo Kα radiation). Both compounds belong to a new structure type (space group P4/mbm, Z = 1, a = 18.7778(2) A, c = 4.0897(1) A (I) and a = 18.7777(3) A, c = 4.0891(1) A (II)) closely related to the Er36Pt102−xSi32 (x = 2.6) type of structure (space group P42/mnm, Z = 1, a = 18.6723 A, c = 8.1734 A). Coordination numbers for three crystallographically independent Dy and Y atoms are 18, 15 and 12 and for Pt atoms range from 9 to 12, distorted cuboctahedra being typical for most of the Pt-atom polyhedra. Triangular prisms with three additional atoms are characteristic for coordination polyhedra of silicon atoms. The peculiarity of the defects of the Pt and Si atom positions as well as the relationship with the Er36Pt102−xSi32 structure is discussed.

The new ternary indides CePd 2 In 4 and CePt 2 In 4 were synthesized by arc-melting of the elements and subsequent annealing at 770 K for 1 month. The crystal structure of both the compounds was refined from the single crystal X-ray data. CePd 2 In 4 and CePt 2 In 4 crystallize in the orthorhombic NdRh 2 Sn 4 -type structure (space group Pnma), a = 18.449(3) A, b = 4.5647(6) A, c = 7.4145(15) A, V = 624.4(2)A 3 , R F = 5.96% for CePd 2 In 4 , a = 18.460(4) A, b = 4.5299(13) A, c = 7.2670(16) A, V = 607.7(3) A 3 , R F = 7.47% for CePt 2 In 4 .