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The intermetallic compounds RE 6 Co 5 Ge 1+x Al 3−x (RE=Pr , Nd) were synthesized from the reaction of germanium and aluminum in RE/Co eutectic flux. These phases crystallize with the Nd 6 Co 5 Ge 2.2 structure type in hexagonal space group P -6 m 2 ( a =9.203(2)A, c =4.202(1) A, R 1 =0.0109 for Pr 6 Co 5 Ge 1.80 Al 2.20 ; and a =9.170(3) A, c =4.195(1) A, R 1 =0.0129 for Nd 6 Co 5 Ge 1.74 Al 2.26 ). The structure features chains of face-sharing Ge@RE 9 clusters intersecting hexagonal cobalt nets linked by aluminum atoms. Magnetic susceptibility measurements indicate that both phases exhibit ferromagnetic ordering of the cobalt layers with T C in the range of 130–140 K. The magnetic moments of the rare earth ions order at lower temperature (30–40 K). Magnetic measurements on oriented crystals of Nd 6 Co 5 Ge 1.74 Al 2.26 show a strong preference of the moments to order along the c -axis.

The germanides Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6} as well as the stannide Ba{sub 3}Sn{sub 2} were prepared by arc melting and annealing in welded tantalum ampoules using induction as well as resistance furnaces. The compounds were investigated by powder and single crystal X-ray diffraction. Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6} crystallize in the Ca{sub 7}Sn{sub 6} structure type (space group Pmna, Z=4: a=7.777(2) A, b=23.595(4) A, c=8.563(2) A, wR{sub 2}=0.081 (all data), 2175 independent reflections, 64 variable parameters for Sr{sub 7}Ge{sub 6} and a=8.0853(6) A, b=24.545(2) A, c=8.9782(8) A, wR{sub 2}=0.085 (all data), 2307 independent reflections, 64 variable parameters for Ba{sub 7}Ge{sub 6}). Ba{sub 3}Sn{sub 2} crystallizes in an own structure type with the space group P4{sub 3}2{sub 1}2, Z=4, a=6.6854(2) A, c=17.842(2) A, wR{sub 2}=0.037 (all data), 1163 independent reflections, 25 variable parameters. In Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6} the Ge atoms are arranged as Ge{sub 2} dumbbells and Ge{sub 4} four-membered atom chains. Their crystal structures cannot be rationalized according to the (8-N) rule. In contrast, Ba{sub 3}Sn{sub 2} presents Sn{sub 2} dumbbells as a main structural motif and thereby can be described as an electron precise Zintl phase. The chemical bonding situationmore » in these structures is discussed on the basis of partial and total Density Of States (DOS) curves, band structures including fatbands, topological analysis of the Electron Localization Function (ELF) as well as Bader analysis of the bond critical points using the programs TB-LMTO-ASA and WIEN2K. While Ba{sub 3}Sn{sub 2} reveals semiconducting behaviour, all germanides Ae{sub 7}Ge{sub 6} (Ae=Ca, Sr, and Ba) show metallic properties and a considerable {pi}-bonding character between the Ge atoms of the four-membered chains and the dumbbells. The {pi}-bonding character of the germanides is best reflected by the resonance hybrid structures {l_brace}[Ge-Ge]{sup 6-}/[Ge-{sup ....}Ge-{sup ....}Ge-{sup ....}Ge]{sup 8-}{r_brace}{r_reversible}{l_brace}[Ge=Ge]{sup 4-}/[Ge-Ge-Ge-Ge]{sup 10-}{r_brace}. - Graphical abstract: The structure of Ba{sub 3}Sn{sub 2} contains Sn{sub 2} dumbbells as a main structural motif and thereby can be described as an electron precise Zintl phase. Ge{sub 2} dumbbells and Ge{sub 4} four-membered atom chains are the predominant features in Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6}. Their crystal structures cannot be rationalized according to the (8-N) rule. While Ba{sub 3}Sn{sub 2} reveals semiconducting behaviour, the germanides Ae{sub 7}Ge{sub 6} (Ae=Ca, Sr, and Ba) show metallic properties and a considerable {pi}-bonding character between the Ge atoms of the four-membered chains and the dumbbells. Highlights: Black-Right-Pointing-Pointer The germanides Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6} as well as the stannide Ba{sub 3}Sn{sub 2} have been synthesized. Black-Right-Pointing-Pointer In Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6} the Ge atoms are arranged as dumbbells and four-membered atom chains. Black-Right-Pointing-Pointer Ba{sub 3}Sn{sub 2} presents Sn{sub 2} dumbbells as a main structural motif. Black-Right-Pointing-Pointer The chemical bonding situation within these structures is discussed.« less

Phase relations have been established by electron probe microanalysis (EPMA) and X-ray powder diffraction (XPD) for the Sr-poor part of the ternary systems Sr–Zn–Si at 800 °C and Sr–Zn–Ge at 700 °C. In the Sr–Zn–Si system one new ternary compound SrZn 2+ x Si 2− x (0≤ x ≤0.45) with CeAl 2 Ga 2 structure and a statistical mixture of Zn/Si in the 4 e site was found. Neither a type-I nor a type-IX clathrate phase was encountered. This system is characterized by formation of two further phases, i.e. SrZn 1− x Si 1+ x with ZrBeSi-type (0.16≤ x ≤0.22) and SrZn 1− x Si 1+ x with AlB 2 -type (0.35≤ x ≤0.65) with a random distribution of Zn/Si atoms in the 2 c site. For the Sr–Zn–Ge system, the homogeneity regions of the isotypic phases SrZn 1− x Ge 1+ x with ZrBeSi-type (0≤ x ≤0.17) and AlB 2 -type (0.32≤ x ≤0.56), respectively, have been determined. Whereas the germanide SrZn 2+ x Ge 2− x (CeAl 2 Ga 2 -type) is characterized by a homogeneity region (0≤ x ≤0.5), the clathrate type-I phase Sr 8 Zn 8 Ge 38 shows a point composition.

The new compounds U{sub 3}Co{sub 12-x}X{sub 4} with X=Si, Ge were prepared by direct solidification of the corresponding liquid phase, followed by subsequent annealing at 1173 K. Single crystal X-ray diffraction carried out at room temperature showed that they crystallize with the hexagonal space group P6{sub 3}/mmc (no.194) and the unit-cell parameters a=8.130(5), c=8.537(5) A and a=8.256(1), c=8.608(1) A for the silicide and germanide, respectively. Their crystal structure derives from the EuMg{sub 5.2} structure type, and is closely related to the Sc{sub 3}Ni{sub 11}Si{sub 4} and Gd{sub 3}Ru{sub 4-x}Al{sub 12+x} types. For the present compounds, no substitution mechanisms have been observed, the partial occupancy of one Co site results from the presence of vacancies, only. The homogeneity ranges, evaluated by energy dispersive spectroscopy analysis, extend from x=0.0(2) to 0.3(2) and from x=0.0(2) to 1.0(2) for U{sub 3}Co{sub 12-x}Si{sub 4} and U{sub 3}Co{sub 12-x}Ge{sub 4}, respectively. The electronic properties of both compounds were investigated by means of DC magnetic susceptibility and DC electrical resistivity measurements. The U{sub 3}Co{sub 12-x}X{sub 4} compounds are both Pauli paramagnets with their electrical resistivity best described as poor metallic or dirty metallic behavior. - Graphical abstract: The crystal structure of the new compounds U{sub 3}Co{sub 12-x}X{submore » 4}, X=Si, Ge is a ternary ordered variant of the EuMg{sub 5.2}-type with a site preference for the 4e position.« less

The ternary rare-earth chromium germanides RECr{sub x}Ge{sub 2} (RE=Sm, Gd-Er) have been obtained by reactions of the elements, either in the presence of tin or indium flux, or through arc-melting followed by annealing at 800 deg. C. The homogeneity range is limited to 0.25{

Two new phases, Yb 1− x Al 3− x Si x and Yb 1− y Al 3− x Ge x , were found by systematic investigations of the according ternary systems. The crystal structures of Yb 1− y Al 2.8 Si 0.2 and Yb 1− y Al 2.8 Ge 0.2 (defect HT-PuAl 3 type) were studied by X-ray powder methods (Cu K α 1 radiation, λ =1.54056 A, hexagonal system, space group P 6 3 / mmc (No. 194), a =6.009(1) and 6.015(1) A, c =14.199(2) and 14.241(5) A, V =444.0(2) and 446.2(3) A 3 , 93 and 92 reflections, and 8200 and 8000 profile points for silicide and germanide, respectively). Full profile refinements with 11 and 13 structural parameters resulted in R I =0.049 and 0.054, and R p =0.088 and 0.104, respectively. The ternary structures are distorted closest packings in comparison with the binary YbAl 3 compound with AuCu 3 -type structure. They are characterized by the formation of Al 3 -, Si 3 -, and Ge 3 -homoatomic clusters and aluminum networks. Magnetization measurements show that both the silicide and germanide are valence fluctuation compounds with enhanced electronic density of states at the Fermi level similar to the binary YbAl 3 . The characteristic maximum of the magnetic susceptibility increases from ≈120 K for YbAl 3 to ≈140 K for Yb 1− y Al 2.8 Si 0.2 or Yb 1− y Al 2.8 Ge 0.2 and further to ≈150 K for Yb 1− y Al 2.75 Si 0.25 . The S-shape of the electrical resistivity curves is also characteristic of valence fluctuations.

Single crystals of the novel ternary compounds EuZn 2 Si 2 and EuZn 2 Ge 2 were grown from pure gallium, indium, or zinc metal used as a flux solvent. Crystal properties were characterized using X-ray single-crystal analyses via Gandolfi and Weissenberg film techniques and by four-circle X-ray single-crystal diffractometry. The new compounds crystallize with ternary derivative structures of BaAl 4 , i.e., EuZn 2 Si 2 with ThCr 2 Si 2 -type ( a =0.42607(2) nm, c =1.03956(5) nm, I 4/ mmm , R 1 =0.038) and EuZn 2 Ge 2 with CaBe 2 Ge 2 -type ( a =0.43095(2) nm, c =1.07926(6) nm, P 4/ nmm , R 1 =0.067). XAS and magnetic measurements on EuZn 2 Si 2 and EuZn 2 Ge 2 revealed in both compounds the presence of Eu 2+ ions carrying large magnetic moments, which order magnetically at low temperatures. The magnetic phase transition occurs at T N =16 and 7.5 K for the silicide and the germanide, respectively. In EuZn 2 Si 2 there occurs a spin reorientation at 13 K and furthermore some canting of antiferromagnetically ordered moments below about 10 K. In EuZn 2 Ge 2 a canted antiferromagnetic structure is formed just at T N .

In previous publications about the seven ternary equiatomic title compounds only the KHg 2 (CeCu 2 )-type subcells with statistical distribution of the palladium and germanium atoms were reported. However, weak superstructure reflections resulting from an ordered distribution of these atoms are observed in the Guinier powder patterns. A CaCuGe ( α -YbAuGe)-type structure with a tripled subcell b axis was established from the powder patterns for the compounds LaPdGe, CePdGe, PrPdGe, NdPdGe, SmPdGe, and the low-temperature ( α ) modification of GdPdGe. In addition, this structure was refined from single-crystal X-ray diffractometer data of CePdGe: Pnma , a =2190.2(9) pm, b =448.4(2) pm, c =767.3(3) pm, R =0.019 for 396 structure factors and 56 variable parameters. The refinement of this structure for α -GdPdGe resulted in a =2112.3(3) pm, b =440.5(1) pm, c =757.7(1) pm, R =0.022 for 372 F values and 56 variables. The high-temperature ( β ) modification of GdPdGe has a YPdSi-type superstructure with a doubled b axis of the subcell: Pmmn , a =430.3(1) pm, b =1409.9(2) pm, c =757.6(1) pm, R =0.019 for 470 F values and 40 variables. In spite of the long-range order of the palladium and germanium atoms established for the superstructures, the refinements of the occupancy parameters suggest small amounts of Pd/Ge disorder for all compounds. The crystal chemistry of these compounds is briefly discussed. The new germanide Yb 3 Pd 4 Ge 4 was prepared from the elements in a sealed tantalum tube in a high-frequency furnace and its structure was refined from single-crystal X-ray data: Gd 3 Cu 4 Ge 4 type, Immm , a =410.7(1) pm, b =707.0(1) pm, c =1372.2(3) pm, R =0.027 for 667 F values and 23 variables.

La4(C2)2Ge was obtained as a minor component from the reaction of the elements in corundum crucibles enclosed in stainless steel ampoules at 1360 K. The compound is gray with metallic luster. The crystal structure (space group I 4 3d (No. 220); a=8.995(1) A; Z=4; R(F)=0.033, Rw(F2)=0.061 for 106 reflections (all data) with 2θmax=50° measured on four-circle diffractometer) may be described as a 3D framework of condensed La8 dodecahedra (bisdisphenoids) centered by Ge atoms and C2 dumbbells (d(C–C)=1.22 A). La4(C2)2Ge and the previous reported cubic compounds La2C3≙La4(C2)3, “La5C1.5Ge3” ≙La4(C2)0.60Ge2.40, and La4Ge3 demonstrate the existence of a large range of homogeneity La4[(C2)1−xGex]3 between the yellow transparent ethenide (4-) La2C3 and La4Ge3. In the series, the C2 dumbbells are replaced by Ge atoms, corresponding with the formal charges C4−2, Ge4−, and La3+. These mixed crystals (Pearson symbol cI28⇔40) represent a continuous transition between the structure types cI40 (Rb4O6/Pu2C3) and cI28 (Th3P4). The results are discussed together with the general trends in the members of both structures types.

An electon and X-ray diffraction investigation of powder and single crystals shows that U 3 Co 4 Ge 7 crystallizes in a tetragonal structure with the space group I 4/ mmm ,: a = 410.87(7) pm, c = 2747.7(9) pm, V = 0.4638(2) nm 3 , Z = 2, R = 0.039 for the Rietveld refinement, and R = 0.050 for the single-crystal study (373 F values and 21 variables). Its structure shows some similarities with that of Eu 2 Pt 7 AlP 4- x and can be interpreted as an intergrowth of CaBe 2 Ge 2 - and Cu 3 Au-type blocks. U 3 Co 4 Ge 7 orders ferro- or ferrimagnetically at 21.5(5) K and exhibits another magnetic transition below 20.5(3) K. Its properties are compared to those observed for other ternary germanides such as UCo 2 Ge 2 and UCoGe.

Recently the crystal structure of a germanium-rich dysprosium germanide (DyGe[sub 3]) has been reported. Significant bonding interactions are present between the germanium atoms in the structure. One type of germanium forms kinked infinite chains [sup 1][sub [proportional to]][Ge]. The remaining two germanium atoms form dimers, stacked in a two-dimensional array as [sup 2][sub [proportional to]][Ge[sub 2]]. DyGe[sub 3] raises intriguing questions concerning stability and bonding; these are investigated with the aid of extended Hueckel calculations. Ge atoms receive electrons from Dy, and Ge states dominate below the Fermi level. There is an interesting electron balance between the two Ge sublattices. The Ge[sub 2] layers contain one additional electron, making them formally a Ge[sup [minus][sub 2]] double layer; the one-dimensional Ge chains contain two extra electrons, fitting the typical Zintl picture as Ge[sup 2[minus]]. The Ge[sub 2] double layers exhibit two-center bonding in the pairs, perpendicular to an electron difficient multicenter bonding system within the layers. The latter is responsible for the expected two-dimensional metallic conductivity.

The new germanium-rich manganese germanide, Mn3Ge5, was synthesized at 600–1000°C and 4 GPa using a Belt-type apparatus. The crystal structure of Mn3Ge5 was identified as possessing the Mn11Si19 type with a tetragonal cell (Schoenflies symbolD2d). The electrical resistivity of Mn3Ge5 increased with increasing temperature and saturated above 200 K. The thermoelectric power was 50–70 μV/K and its sign was positive. These data indicated that Mn3Ge5 was ap-type semiconductor or a semimetal.