  This paper investigates a model containing $\phi^4$ kinks interacting with
fermions. The fermion back-reaction is included in the equations of motion,
which affects the kink-antikink collisions. We show that the fermion field
generates a force that can be either attractive or repulsive. Moreover, we
investigate three different scenarios, which exhibit a wide variety of
behaviors including the usual scenarios observed in the $\phi^4$ model as well
as the formation of two oscillons, reflection without contact, one-bounce
resonance windows, and the creation of kink-antikink pairs. We also find
evidence that the fermion field can store part of the energy responsible for
the energy exchange mechanism.
