Crystal structure of the NdCo4B4 compound and its analogues

The crystalline structure of a new compound NdCo4B4 belonging to a new structural type has been determined by the single crystal method: tetragonal structure, space group P42/n, N=2, rhosub(exp)=7.31 g/cm3, a=7.070, c=3.822 A. Atoms occupy the following positions Nd 2 (b)1/4 1/4 3/4; Co 8 (g) xyz (x=0.607, y=0.125, z=0.138); B 8 (g) (x=O.525, y=0.400, z=0.125); for 46 reflections hkO R=9.7%; 49 reflections hk1 R=7.4 7.4% and 32 reflections hOl R=7.8%. Coordination numbers of Nd, Co and B atoms are 18, 10 and 6 respectively; the coordination polyhedron of boron atoms is a trigonal bipyramid with an additional boron atom opposite one of the crystal faces. In the structure of NdCo4B4 boron atoms are bonded pair-wise. PrCo4B4 and SmCo4B4 are isostructural with NdCo4B4. The already known compound LaCo2B3 also has a NdCo4B4-type structure and it corresponds to composition LaCo4B4