Synthesis, structure, magnetic and photoelectric properties of Ln3M0.5M′Se7 (Ln = La, Ce, Sm; M = Fe, Mn; M′ = Si, Ge) and La3MnGaSe7

Six isostructural new compounds (La₃Fe_0.5GeSe₇, La₃MnGaSe₇, Ce₃Fe_0.5SiSe₇, Ce₃Mn_0.5SiSe₇, Sm₃Fe_0.5SiSe₇ and Sm₃Mn_0.5GeSe₇) have been successfully synthesized.