  The effect of scattering of conduction electrons by dynamical spin
fluctuations on the thermopower in metals near a thermal phase transition into
an antiferromagnetic phase is considered. We are interested in a transition at
room temperature, as has been studied in a heterostructure involving layers of
IrMn. We show that the electrical resistivity exhibits a narrow but low peak at
the transition, which may be difficult to detect on top of the main
contributions induced by phonons and impurities. By contrast, the thermopower
is found to exhibit a prominent peak both as a function of temperature T for
fixed layer thickness tAFM and as a function of tAFM for fixed T: We conjecture
that the transition temperature Tc is a function of both tAFM and the Fermi
energy EF . Both dependencies give rise to a sharp peak of the thermopower as a
function of T or tAFM near the transition. The estimated magnitude of the peak
for the case of three-dimensional longitudinal spin fluctuations is in good
agreement with experiment.
