<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Ln<sub>3</sub>CuGaS<sub>7</sub> and Ln<sub>3</sub>CuGaSe<sub>7</sub> (Ln: La—Nd) are prepared by heating stoichiometric amounts of the elements (evacuated silica tubes, 1050 °C (sulfides)/900 °C (selenides), 5 d).</p> </abstract>