  The electric and magnetic polarizations as well as the electric and magnetic
susceptibilities of the Hubbard pair-cluster embedded in the external fields
were studied by the exact method. Based on the grand canonical ensemble for
open system, the numerical calculations were performed for the electron
concentration corresponding to the half-filling case. It has been found that
the electric and magnetic properties are strictly interrelated, what
constitutes a manifestation of a magnetoelectric effect, and the detailed
explanation of such behaviour was given. In particular, near the ground state
where the transitions are induced by the external fields, discontinuous changes
of the studied quantities have been found. They have been associated with the
occurrence of the singlet-triplet transitions. An anomalous behaviour of the
electric and magnetic polarizations as a function of the temperature, occurring
below the critical magnetic field, was illustrated. In the presence of the
competing electric and magnetic fields, the influence of Coulombic repulsion on
the studied properties was discussed.
