  In this review article we present a survey of unconventional superconductors
and their coexistence behaviour with magnetism.
  We focus on Ce- and U-based heavy fermion superconductors, in addition we
discuss the rare earth borocarbide and skutterudite superconductors. We show
that heavy fermion behaviour in Ce- and U- compounds should be described
differently. While the Kondo-lattice model with localised 4f-electrons is
appropriate for Ce-compounds, dual models including localised and itinerant
5f-electrons are necessary for U-compounds. We demonostrate that this leads to
consistent results for Fermi surface topology and mass enhancement in various
U-compounds. We also show that virtual exchange of localised 5f-electron
excitations provides a new mechanism for unconventional superconductivity in
addition to the known itinerant spin-fluctuation exchange mechanism. We discuss
symmetry properties and coexistence of unconventional superconducting and
density wave (hidden) order parameters and methods for their detection, notably
the new angle resolved magntetotransport methods. The latter have been very
succesful for the investigtion of gap anisotropies in the nonmagnetic
borocarbide superconductors. Recent results on the new multiphase
Pr-skutterudite superconductor are also reviewed.
