Structure cristalline de Tm4Mn4Sn7, le premier stannure isotype de Zr4Co4Ge7

Abstract The crystal structure of Tm 4 Mn 4 Sn 7 was determined on a single crystal. It is of the Zr 4 Co 4 Ge 7 type with space group 14/mmm and : a = 14,880(3) A ; c = 5,837(1) A ; V = 1292 A 3 ; Z = 4; Dx = 8,87 g.cm −3 ; μ (AgK α ) = 23,6 mm −1 ; F(000) = 2903; R = 0,033 (Rw = 0,032) for 256 independant reflexions. This new stannide was compared with the already known isostructural compounds M 4 M′ 4 X 7 (X = Si, Ge). The X atoms are always strongly bound with each of the M and M′ metallic atoms. There are only weak interactions in the X 4 -X 4 chains. The nature of the short X 3 -X 3 pairs is not cleared up; by the available data, these may result from structural constraints as well as from a strong bonding.