Electronic correlation effects observed in compounds formed by transition metals carrying itinerant d
electrons and rare-earth (RE
) metals with more localized f
electrons are one of the central topics in solid-state chemistry and physics. These effects give rise to unusual behaviors, such as mixed and intermediate valence states, heavy fermion and non-Fermi liquid behaviors, superconductivity, Kondo insulators, Kondo semiconductors, quantum criticality, etc. Here we give a short overview of a selection of compounds which have been recently studied.