  In this work we study some physical phenomena that emerge in the vicinity of
a magnetoelectric boundary. For simplicity, we restrict to the case of a planar
boundary described by a coupling between the gauge field with a planar external
Chern-Simons-like potential. The results are obtained exactly. We compute the
correction undergone by the photon propagator due to the presence of the
Chern-Simons coupling and we investigate the interaction between a stationary
point-like charge and the magnetoelectric boundary. In the limit of a perfect
mirror, where the coupling constant between the field and the potential
diverges, we recover the image method. For a non perfect mirror, we show that
we have an attenuated image charge and, in addition, an image magnetic monopole
whose field strength does not exhibit the presence of the undesirable and
artificial divergences introduced by Dirac strings. We also study the
interaction between the plate and a quantum particle with spin. In this case we
have a kind of charge-magnetic dipole interaction due to the magnetoelectric
properties of the plate.
