Structural properties and superconductivity in the ternary intermetallic compounds MAB (M=Ca, Sr, Ba; A=Al, Ga, In; B=Si, Ge, Sn)

The ternary intermetallic compounds MAB=CaAlSi, SrAlSi, BaAlSi, CaGaSi, SrGaSi, BaGaSi, SrAlGe, BaAlGe, CaGaGe, SrGaGe, BaGaGe, BaInGe, BaAlSn, CaGaSn, SrGaSn, and BaGaSn have been prepared by arc-melting stoichiometric elemental mixtures and structurally characterized by a combination of x-ray powder and electron diffraction. They crystallize as variants of the simple hexagonal AlB2 structure type where trivalent and tetravalent A- and B-type atoms, respectively, form commonly a planar hexagon layer, and structural variations arise from A/B ordering and/or puckering of hexagon layers. The silicides (B=Si) were previously investigated for their superconducting properties. By dc magnetization measurements it is demonstrated that also the germanides SrAlGe, BaAlGe, SrGaGe, and BaGaGe and the stannide BaAlSn are superconductors above 2 K.