Thermopower of ruthenium metallic oxides: Large influence of the spin degeneracy term

The thermoelectric properties of ruthenates have been investigated. All the materials studied here are metallic. Thermopower measurements up to high T show that, even if SrRuO₃ is metallic up to 800 K, the Seebeck coefficient of SrRuO₃ is constant from 160 K to 800 K, close to +33 muV/K. Different substitutions have been investigated, and the thermopower is almost not affected by the different substitutions, remaining constant from ~200-300 K up to 800K, close to +25-+35 muV/K. The same result is obtained in CaRuO₃ and derived compounds. Surprisingly, the value of S is close to the theoretical value calculated from spin entropy term only