Superconductivity in silicon and germanium polyhedra

Superconductivity is observed both in silicon and germanium polyhedral materials in Ba24Si100 and Ba24Ge100. The former superconducts at T-c = 1.4 K and its T-c decreases upon pressure, while the latter is superconducting at 150 mK after the electronic phase transition at 200 K and its T-c rises to 3.8 K with pressure. These characteristics are comparably discussed from the viewpoint of the density of states at the Fermi level experimentally derived both in Ba24Si100 and Ba24Ge100 from soft X-ray photoelectron spectroscopy and magnetic susceptibility measurements. (C) 2009 Elsevier B.V. All rights reserved.