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Abstract:
The enhanced thermopower of the correlated semiconductor FeSi is found
to be robust against the sign of the relevant charge carriers. At T
approximate to 70 K, the position of both the high-temperature shoulder
of the thermopower peak and the nonmagnetic-enhanced paramagnetic
crossover, the Nernst coefficient. assumes a large maximum and the Hall
mobility mu(H) diminishes to below 1 cm(2)/V s. These cause the
dimensionless ratio nu/mu(H) -a measure of the energy dispersion of the
charge scattering time tau (epsilon)-to exceed that of classical metals
and semiconductors by two orders of magnitude. Concomitantly, the
resistivity exhibits a hump and the magnetoresistance changes its sign.
Our observations hint at a resonant scattering of the charge carriers at
the magnetic crossover, imposing strong constraints on the microscopic
interpretation of the robust thermopower enhancement in FeSi.
