Syntheses and crystal structures of the quaternary uranium lanthanide oxyselenides UYb2O2Se3 and U2Ln2O4Se3 (Ln=Pr, Sm, Gd)

► Single crystals of the new compounds UYb2O2Se3 and U2Ln2O4Se3 (Ln=Pr, Sm, Gd) have been synthesized. ► These compounds represent the first examples of quaternary uranium oxyselenides. ► U is surrounded by a dodecahedron or square prism of four O atoms and four Se atoms