Potassium aqua­terbium(III) oxalate sulfate

Single crystals of KTb(C(2)O(4))(SO(4))(H(2)O), potassium aqua­terbium(III) oxalate sulfate, were obtained under hydro­thermal conditions. In the crystal structure, the Tb(III) atom is coordinated by four O atoms from two oxalate anions, three O atoms from three sulfate anions and one O atom from a water mol­ecule within a TbO(8) distorted square antiprismatic coordination. The potassium and terbium(III) atoms are bridged by the oxalate and sulfate groups, forming a three-dimensional structure. The coordination mode of the oxalate has not yet been reported. O—H⋯O hydrogen bonding between the water molecules and the oxygen atoms of oxalate and sulfate anions is also observed.