Nontrivial Fermi surface topology in kagome superconductor CsTi₃Bi₅ revealed by de Haas–van Alphen oscillation

The kagome lattice, naturally encompassing Dirac fermions, flat bands, and van Hove singularities, tends to intertwine exotic electronic states. Revealing the characteristics of its Fermi surface will help clarify the nature of the complex quantum phenomena in kagome material. Here we report the Fermi surface properties of the novel kagome metal CsTi₃Bi₅ by the de Haas–van Alphen oscillations. The observed oscillations are clear and consist of six principal frequencies ranging from 214 T to 1013 T. The angular dependence of the frequency implies a quasi-two-dimensional electronic structure. In addition, the geometry phase corresponding to 281 T, determined by direct Lifshitz–Kosevich formula fitting, yields a value close to π, which may indicate a band structure with nontrivial topological property. These results underscore the potential of CsTi₃Bi₅ as a promising platform to explore the interplay between topological order, electronic nematicity, and superconductivity.