TbNb₆Sn₆: The first ternary compound from the rare earth-niobium-tin system

The title compound, terbium hexa-niobium hexastannide, TbNb ₆Sn₆, is the first ternary compound from the rare earth-niobium-tin system. It has the HfFe₆Ge₆ structure type, which can be analysed as an inter-growth of the Zr₄Al ₃ and CaCu₅ structures. All the atoms lie on special positions; their coordination geometries and site symmetries are: Tb (dodeca-hedron) 6/mmm; Nb (distorted icosa-hedron) 2mm; Sn (Frank-Caspar polyhedron, CN = 14-15) 6mm and 6̄m2; Sn (distorted icosa-hedron) 6̄m2. The structure contains a graphite-type Sn network, Kagome nets of Nb atoms, and Tb atoms alternating with Sn2 dumbbells in the channels.