  We extend the semiclassical two-step model [Phys. Rev. A 94, 013415 (2016)]
to include a multielectron polarization-induced dipole potential. Using this
model we investigate the imprints of multielectron effects in the momentum
distributions of photoelectrons ionized by a linearly polarized laser pulse. We
predict narrowing of the longitudinal momentum distributions due to electron
focusing by the induced dipole potential. We show that the polarization of the
core also modifies interference structures in the photoelectron momentum
distributions. Specifically, the number of fanlike interference structures in
the low-energy part of the electron momentum distribution may be altered. We
analyze the mechanisms underlying this interference effect. The account of the
multielectron dipole potential seems to improve the agreement between theory
and experiment.
