Synthesis and crystal structures of La3MgBi5 and LaLiBi2

Two new ternary bismuthides, La3MgBi5 and LaLiBi2, have been prepared by solid-state reactions of the corresponding pure metals in welded niobium tubes at high temperature. Their structures have been established by single-crystal X-ray diffraction studies. La3MgBi5 crystallizes in the hexagonal space group P63/mcm (No.193) with cell parameters of image, image, image, and image. LaLiBi2 belongs to tetragonal space group P4/nmm (No.129) with cell parameters of image, image, image, and image. The structure of La3MgBi5 is of the ‘‘anti’’ Hf5Sn3Cu type, and features 1D linear Bi− anionic chains and face-sharing [MgBi6/2]7− octahedral chains. The structure of LaLiBi2 is isotypic with HfCuSi2, and is composed of 2D Bi− square sheets and 2D LiBi layers with La3+ ions as spacers. Band calculations indicate that both compounds are metallic.