Paradigm for Finding d-Electron Heavy Fermions: The Case of Cr-doped CsFe_{2}As_{2}.

We define a general strategy for finding new heavy-fermionic materials without rare-earth elements: doping a Hund metal with pronounced orbital-selective correlations towards half-filling. We argue that in general band structures, a possible orbital-selective Mott transition is frustrated by interorbital hopping into heavy-fermion behavior-where d orbitals provide both the heavy and the light electrons-which is enhanced when approaching half-filling. This phase ultimately disappears due to magnetic correlations, as in a standard Doniach diagram.