  Motivated by recent experimental results reporting anomalous drag resistance
behavior in dilute bilayer two-dimensional (2D) hole systems in the presence of
a magnetic field parallel to the 2D plane, we have carried out a many-body
Fermi liquid theory calculation of bilayer magnetodrag comparing it to the
corresponding single layer magnetoresistance. In qualitative agreement with
experiment we find relatively similar behavior in our calculated magnetodrag
and magnetoresistance arising from the physical effects of screening being
similarly modified ("suppressed") by carrier spin polarization (at "low" field)
and the conductivity effective mass being similarly modified ("enhanced") by
strong magneto-orbital correction (at "high" fields) in both cases. We
critically discuss agreement and disagreement between our theory and the
experimental results, concluding that the magnetodrag data are qualitatively
consistent with the Fermi liquid theory.
