  It is pointed out that in ferromagnetic metals a contribution to the Hall
voltage arises when a non-zero spin current exists, which is generally the case
in the presence of a charge current. This contribution is independent of any
scattering effects and exists down to zero temperature. The sign of the
resulting Hall coefficient may be either equal or opposite to the one of the
ordinary Hall coefficient depending on the band filling. This effect seems to
have been left out in previous analyses of the Hall effect in ferromagnetic
metals.
