Crystal Structure, Specific Heat, and 119Sn Mössbauer Spectroscopy of CeRu 4Sn 6: A Ternary Stannide with Condensed, Distorted RuSn 6Octahedra

CeRu ₄Sn ₆was prepared from the elements by a reaction in an arc-melting furnace and subsequent annealing at 1123 K. It crystallizes with the tetragonal YRu ₄Sn ₆type structure of space group Ioverline42 m: a=688.1(1), c=975.2(2) pm, V=0.4617(1) nm ³, w R2=0.0472, 554 F²values, and 19 variables. The cerium atoms in CeRu ₄Sn ₆have coordination number 16 formed by 12 tin and 4 ruthenium atoms. These polyhedra are arranged in a tetragonal body-centered packing and are linked by common Sn1 atoms. The strongest bonding interactions are between ruthenium and tin atoms. The ruthenium atoms have 6 tin neighbors at distances from 256.9 to 276.8 pm in the form of a strongly distorted octahedron. Four of such octahedra are condensed via common edges and faces forming [Ru ₄Sn ₆] units. These groups are packed in a tetragonal body-centered arrangement. The cerium atoms occupy the space between the [Ru ₄Sn ₆] units. The [Ru ₄Sn ₆] substructure of CeRu ₄Sn ₆is discussed in comparison with the structures of Ru ₂Sn ₃, LaRuSn ₃, and Ru ₃Sn ₁₅O ₁₄which also contain condensed RuSn ₆octahedra or trigonal prisms as characteristic structural motifs. Despite the two different tin sites the ¹¹⁹Sn Mössbauer spectroscopic measurements show only one signal at δ=1.99 mm/s subjected to quadrupole splitting. Heat capacity measurements indicate that CeRu ₄Sn ₆behaves like a heavy-fermion compound.