  The non-local dielectric response theory is extended to describe oblique
reflection of light from quantum wells subjected to the magnetic field. This
allows us to calculate the dispersion and polarization of the exciton-polariton
modes in semiconductor microcavities in the presence of a magnetic field normal
to the plane of the structure. We show that due to the interplay between the
exciton Zeeman splitting and TE-TM splitting of the photon modes, four
polariton dispersion branches are formed with a polarization gradually changing
from circular in the exciton-like part to linear in the photon-like part of
each branch. Faraday rotation in quantum microcavities is shown to be strongly
enhanced as compared with the rotation in quantum wells.
