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Ternary phases R 5 Li x M 3 were prepared in two ways, by melting and by electrochemical lithiation of the binary compounds R 5 M 3. They crystallize in the hexagonal Hf 5 CuSn 3 structure type, an ordered superstructure of the Mn 5 Si 3 type. Metallic type of bonding was suggested by the analysis of the interatomic distances and confirmed by electronic structure calculations. Electrochemical lithiation reactions of electrodes made of R 5 M 3 alloys were studied in an organic electrolyte containing LiPF 6 salt, using the conventional charge-discharge technique, and the reaction products were analyzed by X-ray powder diffraction. The partially lithiated phase, R 5 Li x M 3 (where x < 0.4), appears to be a solid solution of Li in the initial structure of the binary compounds R 5 M 3. Intermetallic compound / Crystal structure / Rare-earth elements / Lithium / Electrochemistry

The new terbium (lithium zinc) distannide, TbLi1–xZnxSn2 (x = 0.2) crystallizes in the ortho­rhom­bic CeNiSi2 structure type with space group Cmcm and Pearson symbol oS16. Of the four independent 4c atom positions (m2m site symmetry), three are fully occupied by individual atoms (two by Sn and one by Tb atoms) and the fourth is occupied by Li and Zn atoms with a statistical distribution. The Tb coordination polyhedron is a 21-vertex pseudo-Frank–Kasper polyhedron. One Sn atom is enclosed in a tricapped trigonal prism, the second Sn atom is in a cubocta­hedron and the statistically distributed (Li,Zn) site is in a tetra­gonal anti­prism with one added atom. Electronic structure calculations were used for the elucidation of reasons for and the ability of mutual substitution of lithium and transition metals. Positive charge density was observed around the rare earth atom and the Li and Zn atoms, the negative charge density in the proximity of the Sn atoms.

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Key indicators: single-crystal X-ray study; T = 293 K; mean (Tb-Sn) = 0.001 Å; R factor = 0.021; wR factor = 0.066; data-to-parameter ratio = 15.4.The new ternary phase pentaterbium lithium tristannide, Tb 5 LiSn 3 , crystallizes in the hexagonal Hf 5 CuSn 3 structure type, which is a 'filled' version of the binary RE 5 Sn 3 phases (Mn 5 Si 3 -type) (RE is rare earth). The asymmetric unit contains two Tb sites (site symmetries 3.2 and m2m), one Li site (site symmetry 3.m) and one Sn site (site symmetry m2m). The 14-vertex Frank-Kasper polyhedra are typical for Li and Tb atoms. The environment of the Sn atom is a pseudo-FrankKasper polyhedron with a coordination number of 13 for the tin atom. One of the Tb atoms is enclosed in a 17-vertex polyhedron. The metallic type of bonding was indicated by an analysis of the interatomic distances. (1989, 1991, 1993). For the magnetic properties of related compounds, see: Tran et al. (2008). Related literature ExperimentalCrystal data