Coexistence of superconductivity and weak ferromagnetism in Rb-doped triphenylbismuthine and tri-<i>p</i>-tolylbismuthine

By using a two-step method - ultrasound treatment and low temperature annealing, we successfully synthesize Rb-doped triphenylbismuthine and tri-p-tolylbismuthine. The dc magnetic measurements show a coexistence of superconductivity at 4.0 K and weak ferromagnetism at 35 K in all synthesized samples, which is strongly supported by the resistivity measurements. The calculated electronic structure indicates that superconductivity is realized by transferring electron from rubidium to carbon atom, and the weak ferromagnetism is produced by nonparallel arrangement of magnetic moments on the phenyl rings. Our study provides a new platform for understanding the interplay between superconductivity and ferromagnetism.