Quantum oscillations and electronic structure in the large-Chern number topological chiral semimetal PtGa

We report the magnetoresistance(MR), de Haas-van Alphen (dHvA) oscillations and the electronic structures of single crystal PtGa. The large unsaturated MR is observed with the magnetic field B//[111]. Evident dHvA oscillations with B//[001] configuration have been observed, from which twelve fundamental frequencies are extracted and the spin-orbit coupling effect (SOC) induced band splitting is revealed. The light cyclotron effective masses are extracted from the fitting by the thermal damping term of the Lifshitz-Kosevich (LK) formula. Combining with the calculated frequencies from the first-principles calculations, the dHvA frequencies F${}_1$/F${}_3$ and F${}_{11}$/F${}_{12}$ are confirmed to originate from the electron pockets at $\mathrm{\Gamma }$ and R, respectively. The first-principles calculations also reveal the existence of spin-3/2 RSW fermion and time-reversal (TR) doubling of the spin-1 excitation at $\mathrm{\Gamma }$ and R with large Chern number $\pm 4$ when SOC is included.