The discovery of compounds with new, unexpected physical properties which challenge established theoretical concepts is an essential driving force in the field of strongly correlated electron systems. The aim of our group is to search for such new systems and to provide experimental groups, both at the MPI-CPfS and worldwide, with appropriate high quality poly- and single-crystalline samples. We look for compounds with unconventional electronic, magnetic or structural properties, which are often, but not always, associated with a quantum critical point, i.e. a second order phase transition tuned to T = 0. One main research fields are intermetallic compounds based either on rare earths with unstable valence (so-called Kondo lattices or heavy fermion systems and valence-fluctuating materials), or based on 3d transition metals close to a magnetic instability. The second main research field is complex oxides based on 3d, 4d, or 5d transition metals which, despite their oxide character, exhibit metallic behavior. Activities range from preparation of polycrystalline samples of new compounds, determination of basic properties to sort out interesting systems, synthesis of high quality samples and single crystals for dedicated experiments, and tuning the compounds by doping according to request of experimental groups. We keep a close interaction with both experimental and theory groups to back up our research.