  We report the temperature $T$ and magnetic field $H$ dependence of the
thermopower $S$ of an itinerant triangular antiferromagnet PdCrO$_2$ in high
magnetic fields up to 32 T. In the paramagnetic phase, the zero-field
thermopower is positive with a value typical of good metals with a high carrier
density. In marked contrast to typical metals, however, $S$ decreases rapidly
with increasing magnetic field, approaching zero at the maximum field scale for
$T >$ 70 K. We argue here that this profound change in the thermoelectric
response derives from the strong interaction of the 4$d$ correlated electrons
of the Pd ions with the short-range spin correlations of the Cr$^{3+}$ spins
that persist beyond the N\'{e}el ordering temperature due to the combined
effects of geometrical frustration and low dimensionality.
