Potassium aqua-terbium(III) oxalate sulfate.

Single crystals of KTb(C(2)O(4))(SO(4))(H(2)O), potassium aqua-terbium(III) oxalate sulfate, were obtained under hydro-thermal 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 mol-ecule 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.