Thermopower of Dilute Alloys of Cerium in Lanthanum

We have measured a large negative peak in the thermoelectric power S of the La–Ce Kondo system at low temperature. This result is qualitatively different than that of Sugawara. Measurements were made in the range 4.2 K≤T≤350 K for four compositions: 0.03-, 0.5-, 2-, and 5-at.% Ce. The size of the peak was in the range −1.5 to −2. μV/K and occurred at ∼20 K. The shape of the curves, and the temperature at which the peak occurred, were nearly independent of composition for T<150 K, while the curves were somewhat sample dependent at higher temperatures. While significant amounts of metallic impurities were present, they probably do not contribute a peak in the thermopower. However, on the basis of these measurements one cannot rule out the possibility that the peak is intrinsic to La.