Twinned caesium cerium(IV) penta­fluoride

Single-crystals of CsCeF₅ were synthesized hydro­thermally. The crystal under investigation was twinned by pseudo-merohedry with a twofold rotation around the c axis as an additional twinning operation. The crystal structure is built of layers of distorted edge- and corner-sharing CeF₈ square-anti­prisms. The Cs⁺ cations are located between the layers and exhibit coordination numbers of nine. Upon compression, CsCeF₅ undergoes an irreversible phase transition at about 1 GPa.