Low-temperature thermopower of (SN)x

Measurements of the thermoelectric power of (SN)x are reported over the temperature range 0.15-4.2 K for magnetic fields of 0-15 kOe applied parallel and perpendicular to the fiber axis. Above 1 K, the thermopower is large, negative, and dominated by phonon drag, which indicates that electrons contribute more to the electrical conductivity than do holes, and that the phonons are predominately scattered by the electrons. As the temperature is decreased below 1 K in zero field, an increase in the thermopower is observed which is attributed to the Kondo effect. This increase is terminated at the superconducting transition temperature, where the thermopower drops to zero. With the application of a magnetic field, a complicated behavior is observed below 1 K which is attributed to a combination of the quenching of superconductivity, superconducting fluctuations, magnetic impurities, and the Kondo effect.