Potassium tetrafluoronickelate is the inorganic compound with the formula K<sub>2</sub>NiF<sub>4</sub>. It features octahedral (high spin) Ni centers with Ni-F bond lengths of 2.006 ÃÂ . This green solid is a salt of tetrafluoronickelate. It is prepared by melting a mixture of nickel(II) fluoride, potassium fluoride, and potassium bifluoride. The compound adopts a perovskite-like structure consisting of layers of octahedral Ni centers interconnected by doubly bridging fluoride ligands. The layers are interconnected by potassium cations. It is one of the principal Ruddlesden-Popper phases. Early discoveries on cuprate superconductors focused on compounds with structures closely related to K<sub>2</sub>NiF<sub>4</sub>, e.g. lanthanum cuprate and derivative lanthanum barium copper oxide.