TbNb(6)Sn(6): the first ternary compound from the rare earth-niobium-tin system.

The title compound, terbium hexa-niobium hexastannide, TbNb(6)Sn(6), is the first ternary compound from the rare earth-niobium-tin system. It has the HfFe(6)Ge(6) structure type, which can be analysed as an inter-growth of the Zr(4)Al(3) and CaCu(5) 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 m2; Sn (distorted icosa-hedron) m2. The structure contains a graphite-type Sn network, Kagome nets of Nb atoms, and Tb atoms alternating with Sn2 dumbbells in the channels.