Fermi surface studies of the topologically nontrivial compound YSi

The Fermi surface properties of a nontrivial system YSi is investigated by de Haas-van Alphen (dHvA) oscillation measurements combined with the first-principle calculations. Three main frequencies ($\alpha$, $\beta$, $\gamma$) are probed up to $14$~T magnetic field in dHvA oscillations. $\alpha$-branch corresponding $21$~T frequency possesses non-trivial topological character $\pi$ Berry phase and linear dispersion along $\Gamma$ $Z$ direction small effective mass $0.069~m_e$ second-lowest Landau-level $14$~T. For $B~\parallel$~[010] direction, 295~T exhibits $2D$ $1.24\pi$ high velocity $6.7 \times 10^5$~ms$^{-1}$. band structure calculations reveal multiple nodal crossings vicinity energy $E_f$ without spin-orbit coupling (SOC). Inclusion SOC opens gap results nonsymmorphic symmetry enforced Dirac points at some points, suggesting be metal.