Unlike cuprates — the first known class of unconventional superconductors — the new nickelates are inherently metallic, sharing electrons with intervening layers of rare earth material to create a 3D metallic state. This is an entirely new type of ground state for transition metal oxides such as cuprates and nickelates, researchers said. It opens new directions for experiments and theoretical studies of how superconductivity arises and how it can be optimized in this system and possibly in other compounds.