Synthesis, structure, and superconductivity in Be1.09B3

The compound Be1.09B3 was prepared by arc-melting of the elemental constituents. The structure of single crystals taken from the arc-melted button was determined from single-crystal X-ray data (T = 120 K) and is hexagonal, having space group P6/mmm, and lattice parameters a = 9.7738(7) Angstrom and c = 9.5467(6) Angstrom, R = 0.047. The structure consists of a hexagonal array of boron icosahedra, nonicosahedral B-12 cages, and B-18 cages. Stacked hexagonal layers of boron atoms, hexagons formed by B and Be, and equilateral triangles of boron atoms disordered by a 60degrees rotation exist along a 6-fold axis down the [001] direction. A superconducting transition at 0.72 K is clearly indicated by resistivity measurements. (C) 2002 Elsevier Science.