Structure electronique de quelques hexaborures de type CaB6

Cubic MB6 borides (M = Th, La, Yb, Ca, Sr) have been prepared with a high purity either from the elements or by borothermic reduction of oxides. Magnetic susceptibility, thermoelectric power and specific heat measurements have been done to study the electronic structure of the compounds. All the specimens were sintered at high temperature except LaB6 samples which were zone refined. Hexabordies of elements having an oxidation state higher than two (M = Th, La) exhibit a metallic behavior. In YbB6 ytterbium is divalent. Hexaborides of elements having an oxidation state equal to two (M = Yb, Ca, Sr) are semiconductors. The electronic behavior of the compounds which have been studied agrees with the H. C. Longuet-Higgins and M. de V. Roberts' model.