Ternary laves phases Sc${}_{0.22\left(1\right)}$Ta${}_{0.78\left(1\right)}$Fe${}_2$ and Sc${}_{0.63\left(1\right)}$In${}_{0.37\left(1\right)}$Co${}_2$ - coloring variants of the MgZn${}_2$ and MgNi${}_2$ type

The ternary Laves phases Sc${}_{0.22\left(1\right)}$Ta${}_{0.78\left(1\right)}$Fe${}_2$ and Sc${}_{0.63\left(1\right)}$In${}_{0.37\left(1\right)}$Co${}_2$ were synthesized by arc-melting appropriate amounts of the binary phases ScFe${}_2$ and TaFe${}_2$ or Sc, In and Co, respectively. The samples were studied by powder X-ray diffraction and the structures were refined from single crystal X-ray diffraction data: P6${}_3$/mmc , a=484.96(7), c=793.17(11) pm, wR 2=0.0604, 147 F${}^2$ values, 12 variables for Sc${}_{0.22\left(1\right)}$Ta${}_{0.78\left(1\right)}$Fe${}_2$ and P6${}_3$mc , a=488.61(4), c=1599.54(12) pm, wR 2=0.0389, 553 F${}^2$ values, 35 variables for Sc${}_{0.63\left(1\right)}$In${}_{0.37\left(1\right)}$Co${}_2$. Sc${}_{0.22\left(1\right)}$Ta${}_{0.78\left(1\right)}$Fe${}_2$ derives from the MgZn${}_2$ type having a mixed Sc/Ta occupancy on the 4f magnesium position. Sc${}_{0.63\left(1\right)}$In${}_{0.37\left(1\right)}$Co${}_2$crystallizes with a new structure type which derives from the Laves phase MgNi${}_2$. A translationengleiche symmetry reduction leads to the non-centrosymmetric space group P6${}_3$mc which allows partial Sc/In ordering with different Sc/In ratios on four crystallographically independent sites. While ScFe${}_2$ and TaFe${}_2$ build a complete solid solution Sc${}_{1-x}$Ta${}_x$Fe${}_2$ with MgZn${}_2$ type structure, we observe a switch in structure type for Sc${}_{1-x}$In${}_x$Co${}_2$ from the cubic MgCu${}_2$ type (x=0-0.22) to the non-centrosymmetric derivative from MgNi${}_2$ at x=0.37. (© 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie published by Wiley-VCH GmbH)