(a) Crystal structure of Ba₂BiFeS₅. The white, orange, dark green, and yellow balls represent Ba, Fe, Bi, and S atoms, respectively. (b) Structural unit of an infinite [ FeBiS ] 4 − 1 ∞ chain arranged in the bc plane. The shortest atomic distances of intrachain Fe–Bi and interchain Fe–Fe are marked. (c) Powder XRD pattern of crushed Ba₂BiFeS₅ single crystals. The black and red line represents the observed and calculated pattern, respectively, and the green line shows the difference between them. The black and blue bars represent the peak portions of Ba₂BiFeS₅ and the minor second phase BaBi₂S₄, respectively. (d) The EDX spectrum of Ba₂BiFeS₅ single crystal. Inset: photo of obtained Ba₂BiFeS₅ single crystals. The length of one grid in the photo is 1 mm.