Crystal structure and physical properties of Mg6Cu16Si7-type M6Ni16Si7, for M=Mg, Sc, Ti, Nb, and Ta

Five compounds were investigated for magnetic character and superconductivity, all with non-magnetic nickel and band structures containing flat bands and steep bands. The syntheses and crystal structures, refined by powder X-ray diffraction, are reported for M{sub 6}Ni{sub 16}Si{sub 7}, where M = Mg, Sc, Ti, Nb, and Ta. All compounds form in the Mg{sub 6}Cu{sub 16}Si{sub 7} structure type. Resistance measurements are also reported on M{sub 6}Ni{sub 16}Si{sub 7} (M = Mg, Sc, Ti, and Nb) down to 0.3 K, with all four showing metallic conductivity. No superconductivity is observed. Magnetization measurements for all compounds reveal essentially temperature independent paramagnetism, with a tend…