THERMOPOWER OF AL1-XSIX SOLID-SOLUTIONS IN VICINITY OF LATTICE INSTABILITY

The thermopower coefficient as a function of temperature, S(T), has be en measured in nonequilibrium superconductors, such as Al1-xSix substi tutional solid solutions and Al-Si alloys on various decay stages. Whe n aluminum is substituted with silicon, the contribution to the thermo power due to phonon-drag effects, which are dominant in pure aluminum at low temperatures, is suppressed, and low-temperature anomalies in S (T) detected in compositions near lattice instability limit are determ ined by the diffusion component of the thermopower. The low-temperatur e anomalies in the thermopower and the notable increase in the coeffic ient in front of the linear term in S(T) are attributed to effects of thermopower renormalization due to the electron-phonon interaction enh ancement with ''soft modes'' in the face-centered cubic (FCC) lattice of Al1-xSix solid solutions. The nature of these anomalies in S(T) is analyzed in terms of the Kaiser and Reizer-Sergeev models. (C) 1998 Am erican Institute of Physics.