The crystal structure of Tm6Co26-xIn14 (x=7.42) compound

New ternary indides R6Co26-xIn14 (R=Er,Tm) have been found in the systems { Er,Tm}-Co-In at 870 K. The crystal structure of Tm6Co26-xIn14 (x=7.42) has been refined using single-crystal X-ray data: Lu6Co26-xIn14 (x=8.41) struct ure type, Pm (3) over bar space group, Z=1, a=8.655(4) Angstrom, V=648.4(9) Angstrom(3), R=0.0245 for 233 unique reflections hkl (DARTCH-1 diffractome ter, Mo K alpha radiation). The lattice parameter for the isostructural com pound Er6Co20-xIn14 is a=8.663(1) Angstrom. The coordination polyhedra of t he Tm atoms have 15 vertices, those of the In atoms 12 and 13 vertices and those of the Co atoms eight, ten and 12 vertices. The structure can be desc ribed as a stacking of columns double hexagonal antiprisms with two additio nal atoms opposite the bases, and comprises icosahedra, cubes, trigonal pri sms and empty tetrahedra. (C) 1999 Elsevier Science S.A. All rights reserve d.