  A theoretical study of the magnon-drag Peltier and Seebeck effects in
ferromagnetic metals is presented. A magnon heat current is described
perturbatively from the microscopic viewpoint with respect to electron--magnon
interactions and the electric field. Then, the magnon-drag Peltier coefficient
$\Pi_\MAG$ is obtained as the ratio between the magnon heat current and the
electric charge current. We show that $\Pi_\MAG=C_\MAG T^{5/2}$ at a low
temperature $T$; that the coefficient $C_\MAG$ is proportional to the spin
polarization $P$ of the electric conductivity; and that $P>0$ for $C_\MAG<0$,
but $P<0$ for $C_\MAG>0$. From experimental results for magnon-drag Peltier
effects, we estimate that the strength of the electron--magnon interaction is
about 0.3 eV$\cdot\AA^{3/2}$ for permalloy.
