Anomalous thermoelectric power of rare earth metals and their compounds

We propose a new mechanism for an anomalous thermoelectric power (ATP) in the paramagnetic state of certain rare earth metals and their compounds, in which the ions possess a nonmagnetic ground state in a given crystal field. The ATP is found to be due to higher order inelastic scattering (second Born approximation) of the conduction electrons by the crystal field split rare earth ions. It has a peak at a temperatureΔ/3 ~Δ/2, whereΔ is the splitting energy between the ground state and the first excited state. Our main result is that the appearance of an ATP requires interactions between the conduction electrons and the ions of other than the simple isotropic exchange type. This implies that the ATP may serve as a valuable tool to detect more complicated types of thek-f interaction than the isotropic exchange.