Electronic structure of Si and Ge gold-doped clathrates

The electronic properties of single phase type-I clathrate compounds, Ba8Au 6(Si or Ge)(40) and Ba8Ge46-x have been investigated. The crystal structure , electrical resistivities, magnetic susceptibilities, the density of state s at the Fermi level, and the band gap (where applicable) were determined. Ba8Au6Si40 and Ba8Au6Ge40 show a metallic behavior whereas Ba8Ge46-x is sem iconducting. On a basis of this work, a first evidence is presented of the existence of type-I mixed-clathrates containing both silicon and germanium. [S0163-1829(99)09743-X].