Neue ternäre Germanide: Die Verbindungen Ln4Zn5Ge6 (Ln: Gd,Tm, Lu)

New Ternary Germanides: The Compounds Ln ₄Zn₅Ge₆ ( Ln : Gd, Tm, Lu) Three new ternary germanides were prepared by heating mixtures of the elements. Gd₄Zn₅Ge₆ (a = 4.249(3), b = 18.663(17), c = 15.423(6) Å), Tm₄Zn₅Ge₆ (a = 4.190(1), b = 18.410(5), c = 15.105(5) Å), and Lu₄Zn₅Ge₆ (a = 4.179(1), b = 18.368(4), c = 15.050(3) Å) are isotypic and crystallize in a new structure type (Cmc2₁; Z = 4), composed of edge‐ and corner‐sharing ZnGe₄ tetrahedra. The rare‐earth atoms fill channels of the Zn,Ge network running along the a axis and predominantly have an octahedral coordination of Ge atoms or a pentagonal prismatic environment of Zn and Ge atoms. The ZnGe₄ tetrahedra are orientated to each other so that two of six Ge atoms form pairs, while the other ones have no homonuclear contacts. This is in accord with an ionic splitting of the formula: (Ln³⁺)₄(Zn²⁺)₅(Ge^3–)₂(Ge^4–)₄. LMTO band structure calculations support the interpretation of bondings derived from interatomic distances. The metallic conductivity of these compounds expected from the electronic band structure was confirmed by measurements of the electrical resistance of Tm₄Zn₅Ge₆.