  Within a strongly interacting Fermi liquid framework, we calculate the
effects of the Zeeman energy $\omega_H$ for a finite magnetic field, in a
metallic system with a van Hove peak in the density of states, located close to
and below the Fermi surface. We find that the chemical potential increases with
the square of $\omega_H$. We obtain a characteristic quasiparticle scattering
rate linear in the maximum of $\omega_H$ and temperature, both in the normal
and the d-wave superconducting state. We predict that ARPES experiments in
copper oxides, and related compounds, should be able to elucidate this behavior
of the scattering rate, and in particular, the difference between spin up and
down electrons.
