  The thermoelectric properties of single- and polycrystalline FeGa3 are
systematically investigated over a wide temperature range. At low temperatures,
below 20 K, previously not known pronounced peaks in the thermal conductivity
(400-800 W K^-1m-1) with corresponding maxima in the thermopower (in the order
of -16000 microV/K) were found in single crystalline samples. Measurements in
single crystals along [100] and [001] directions indicate only a slight
anisotropy in both the electrical and thermal transport. From susceptibility
and heat capacity measurements, a structural or magnetic phase transition was
excluded. Using density functional theory-based calculations, we have revisited
the electronic structure of FeGa3 and compared the magnetic (including
correlations) and non-magnetic electronic density of states. Thermopower at
fixed carrier concentrations are calculated using semi-classical Boltzmann
transport theory, and the calculated results match fairly with our experimental
data and exclude the possibility of strong electronic correlations as an
explanation for the low temperature enhancement. Eventually, after a careful
review, we assign the peaks in the thermopower as a manifestation of the
phonon-drag effect, which is supported by thermopower measurements in a
magnetic field.
