Electrical properties of lead telluride single crystals doped with Gd

Temperature dependences of electric conductivity, free carrier concentration and mobility in single-crystalline PbTe: Gd samples with a varied impurity content are investigated. The features of electron transport in PbTe: Gd may be caused by a variable gadolinium valence. The striking result from the Seebeck coefficient measurements is that the thermoelectric power factor increases dramatically. Measurements of the magnetic susceptibility at low temperatures permit us to suggest that Gd ions exist in different charge states.