Heterogeneous Mixed-Valence States in RPd₃S₄ (R=Eu and Yb) Viewed from Thermopower, Electrical Resistivity and Specific Heat

Abstract

Rare-earth palladium bronzes EuPd₃S₄ and YbPd₃S₄ with a crystal structure akin to that of the filled-skutterudite compounds are known to show the heterogeneous mixed-valence state scarcely observed among rare-earth intermetallics. In order to shed light on the state, we have measured the thermopower, electrical resistivity and specific heat. It is found that no enhancement of the density of states near the Fermi level occurs in either compound, unlike the case of homogeneous mixed-valence compounds. The thermopower of both systems is qualitatively interpreted using the two-carrier model of electrons and holes, consistently with the reported data of the Hall effect of EuPd₃S₄.