We have studied the magnetization of a recently synthesized Cu9S5 compound and found two phase transitions around room temperature. The phase transitions in the crystalline structure, characterized by XRD studies, are accompanied by changes also in the electrical resistivity. A hysteretic first-order phase transition has been found between 260 and 320 K, from a low-temperature paramagnetic anilite phase to a diamagnetic high-temperature low-digenite phase. A second order phase transition was recognized at ≃ 352 K from low digenite to a paramagnetic high-digenite structure at high temperatures.
