  We have studied transport and magnetotransport properties of the
heterostructure consisting of the ferroelectric Ba$_{0.8}$Sr$_{0.2}$TiO$_3$
film deposited on the single crystalline manganite LaMnO$_3$. Two-dimensional
electron gas arising at the interface transforms the interface region of the
antiferromagnetic manganite to the ferromagnetic state with the reoriented
magnetic moments. We obtained that the contribution of these ferromagnetic
regions to the resistance of the heterostructure appears to be dependent on the
external magnetic field applied perpendicularly to the interface (and parallel
to {\it c}-axis of the ferromagnetic state of LaMnO$_3$). We believe that the
decrease of the resistance of the studied heterostructure under the influence
of the external magnetic field is caused by an appearance of the ferromagnetic
order in the interface area. This leads to a relatively small resistance. In
turn, the cycling of the applied magnetic field leads to the increase of the
regions of the ferromagnetic order and, as a result, to decreasing scattering
of the current carriers at the ferromagnetic disordering.
