Lithium alkaline earth tetrelides of the type Li2 AeTt (Ae=Ca, Ba, Tt=Si, Ge, Sn, Pb): synthesis, crystal structures and physical properties

Single crystals of the compounds Li2 AeTt (Ae=Ca, Ba, Tt=Si, Ge, Sn, Pb) were grown in reactive lithium melts in sealed tantalum ampoules from an equimolar ratio of the alkaline earth metal and the respective group 4 element. All compounds, with the exception of Li2CaSn and Li2CaPb, are isotypic and crystallize in an orthorhombic unit cell (space group Pmmn, no. 59). The crystal structure can be characterized as superimposed corrugated networks of Li2 Tt connected by calcium or barium atoms within the third dimension. Li2CaSn and Li2CaPb crystallize in the cubic space group Fm3̅m (no. 225) in a Heusler-type (MnCu2Al) structure. According to magnetic susceptibility and electric resistivity measurements, the compounds Li2BaGe, Li2BaSn, and Li2BaPb represent diamagnetic activated semiconductors.