<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Solvothermal reactions of Ln<sub>2</sub>O<sub>3</sub>, As and S in diethylenetriamine (dien) (autoclave, 170 °C, 6 d) yields two structural types of lanthanide thioarsenates of general formulae [Ln(dien)<sub>2</sub>(μ‐1ϰ, 2ϰ<sup>2</sup>‐AsS<sub>4</sub>)] <sub>n</sub> (Ln: Sm, Eu, Gd) and [Ln(dien)<sub>2</sub>(1ϰ<sup>2</sup>‐AsS<sub>4</sub>)] (Ln: Tb, Dy, Ho) in 45—57% yield.</p> </abstract>