  Finite temperature SU(2) lattice gauge theory is investigated in a 3D cubic
box with fixed boundary conditions (b.c.) provided by a discretized, static BPS
monopole solution with varying core scale ${\mu}$. For discrete ${\mu}$-values
we find stable classical solutions either of electro-magnetic ('dyon') or of
purely magnetic type inside the box. Near the deconfinement transition we study
the influence of the b.c. on the quantized fields inside the box. In contrast
to the purely magnetic background field case, for the dyon case we observe
confinement for temperatures above the usual critical one.
