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Abstract:
We optimized the syntheses of - and -Bi4I4 and transferred the method to the very bismuth-rich iodides Bi14I4, Bi16I4, and Bi18I4. Phase-pure, microcrystalline powders of BimI4 (m = 4, 14, 18) can now by synthesized on a multigram scale. Conditions for the growth of single crystals of Bi16I4 and Bi18I4 were determined. The redetermination of the crystal structure of Bi16I4 hints at a stacking disorder or the presence of (1)[BimI4] ribbons with m = 14 and 18 among the dominant type along with m = 16. The electronic band structures for m = 14, 16, and 18 were calculated including spin-orbit coupling. They vary markedly with m and show numerous bands crossing the Fermi level, predicting a 3D-metallic behavior. Measurements of the electrical resistivity of a polycrystalline sample of Bi14I4 as well as polycrystalline and single-crystalline samples of Bi18I4 confirmed their metallic nature over the temperature range 300 K to 2 K. For Bi18I4, a positive and strictly linear magnetoresistance at 2 K in static magnetic fields up to 14 T was observed, which could indicate a topologically nontrivial electronic state.
