Pt₅Mn₂Si, the first platinum-rich ternary intermetallic of the Rh₅Ge₃ structure type: Synthesis, crystal and electronic structure, and magnetic properties

New ternary intermetallic Pt5Mn2Si was obtained in the form of single crystals and phase-pure polycrystalline bulk samples. This compound is only the second one found in the Pt-Mn-Si system. Pt5Mn2Si (space group Pbam, a = 5.4355(3) angstrom, b = 10.5955(7) angstrom, c = 4.0024(3) angstrom, Z = 2) is isotypic with the Rh5Ga2As structure, an ordered ternary variation of the Rh5Ge3 structure type. This structure type is fairly rare, and Pt5Mn2Si is only the second ternary intermetallic adopting this structure. Magnetic measurements show that the compound has magnetic transition at ca. 80 K, most likely attributed to ferrimagnetic ordering of manganese spins. DFT calculations predict Pt5Mn2Si to be a metallic conductor. Chemical bonding analysis shows a pattern of localized pairwise-like Pt-Mn and Pt-Si bonds.