  The discovery of exotic abundances, chemical inhomogeneities, and weak
magnetic fields on the surface of late B-type primaries in spectroscopic
binaries has important implications not only for our understanding of the
formation mechanisms of stars with Hg and Mn peculiarities themselves, but also
for the general understanding of B-type star formation in binary systems. The
origin of the abundance anomalies observed in late B-type stars with HgMn
peculiarity is still poorly understood. The connection between HgMn peculiarity
and membership in binary and multiple systems is supported by our observations
during the last decade. The important result achieved in our studies of a large
sample of HgMn stars is the finding that most HgMn stars exhibit spectral
variability of various chemical elements, proving that the presence of an
inhomogeneous distribution on the surface of these stars is a rather common
characteristic and not a rare phenomenon. Further, in the studied systems, we
found that all components are chemically peculiar with different abundance
patterns. Generally, He and Si variable Bp stars possess large-scale organised
magnetic fields that in many cases appear to occur essentially in the form of a
single large dipole located close to the centre of the star. The presence of
magnetic fields in the atmospheres of HgMn stars has been demonstrated in
several studies. In addition to the measurements of longitudinal and quadratic
magnetic fields, this work also showed evidence for a relative magnetic
intensification of Fe II lines produced by different magnetic desaturations
induced by different Zeeman-split components.
