New Phases in the Sc−Mn−Si and Sc−Mn−Al−Si Systems Through Molten Indium Flux Synthesis

Through the application of synthesis via molten indium flux, we have been able to expand the ternary Sc−Mn−Si system and the quaternary Sc−Mn−Al−Si system. Specifically, we report on five previously unknown chemical compounds, namely β-ScMnSi₂, Sc_4+xMn₄Si_7–2x, Sc₂Mn₄Si₅, Sc₂Mn₃Si₄, and Sc₄Mn₂AlSi₄. The compounds with the stoichiometries Sc₂Mn₄Si₅, Sc₂Mn₃Si₄, and Sc₄Mn₂AlSi₄ have previously not been reported. We find that these crystallize in the V₆Si₅, Hf₂Ru₃Si₄, and Ho₄Ni₂InGe₄ structure types, respectively. For the ternary compounds with the stoichiometries of ScMnSi₂ and Sc_4+xMn₄Si_7–2x, we find clearly deviating structural solutions compared to earlier reports. β-ScMnSi₂ is found to crystallize in the monoclinic crystal system isostructural to a supercell of the MnTiSi₂ structure and clearly deviating from the known orthorhombic α-polymorph. The compound Sc_4+xMn₄Si_7–2x is structurally very similar to Sc₄Mn₄Si₇, but exhibits the P4/nmm space group instead of I4/mmm, and is related to the Zr₄Co₄Ge₇ structure. Disorder between Si and Sc sites leads to the off-stoichiometric composition, for which we found x=0.287(5).