THERMOELECTRIC-POWER OF METALLIC SI(P,B) AT VERY-LOW TEMPERATURES

The thermoelectric power S(T) of metallic compensated Si:(P,B) samples with carrier concentration N = 13.0 and 4.24 . 10(18)cm(-3) has been measured between 0.1 and 10 K. For the more heavily doped sample, the low-T data can be well described with a negative T-linear nearly-free- electron diffusion term and a T-3 phonon-drag contribution. The sample closer to the metal-insulator transition (critical concentration N-c = 3.54 . 10(18)cm(-3) for the compensation ratio of this sample), exhi bits a sign change of S(T) at 0.35 K, becoming positive towards lower T. The ensuing maximum (since S(T --> 0) = 0) is attributed to Kondo s cattering by local magnetic moments. This is supported by the suppress ion of this maximum and recovery of a linear S(T) in a magnetic held o f approximate to 5T.