Superconductivity in Noncentrosymmetric Iridium Silicide Li2IrSi3

The effects of lithium absorption on the crystal structure and electronic properties of IrSi3, a binary silicide with a noncentrosymmetric crystal structure, were studied. X-ray and neutron diffraction experiments revealed that hexagonal IrSi3 (space group P6_3mc) transforms into trigonal Li2IrSi3 (space group P31c) upon lithium absorption. The structure of Li2IrSi3 is found to consist of a planar kagome network of silicon atoms with Li and Ir spaced at unequal distances between the kagome layers, resulting in a polar structure along the c-axis. Li2IrSi3 exhibited type-II superconductivity with a transition temperature Tc of 3.8 K, displaying a structure type that no previous superconductors have been reported to have.