Quantum oscillations in kagome metals (Ti, Zr, Hf)V6Sn6 at van Hove filling
Kagome materials have recently drawn great attention due to the interplay between nontrivial band topology, electron correlations and van Hove singularities related many-body orders. Here we report three new vanadium-based kagome metals, TiV6Sn6, ZrV6Sn6 and HfV6Sn6, and conduct a comprehensive investigation on their structural, magnetic and electrical transport properties. All three compounds exhibit large unsaturated magnetoresistances and multiband Hall effects at low temperatures, indicating the existence of multiple highly mobile carriers. Both the diagonal and off-diagonal resistivity show quantum oscillations with nontrivial Berry phases and high quantum mobilities. First-principles calculations together with quantum oscillation analyses suggest the van Hove singularities at the M point for the three compounds all locate in close vicinity of the Fermi level, and there also exist multiple topological nontrivial band crossings including a nodal ring and a massive Dirac cone. Our work extends the kagome R166 family and paves the way for searching possible van Hove physics in the V kagome lattice.