Multiband quantum oscillations and Kohler's rule in the extremely large magnetoresistance material pyrite PtBi2

We present magnetotransport, Seebeck effect, and magnetic torque measurements conducted on the Dirac semimetal PtBi2 single crystals with a temperature range of 1.8–300 K and magnetic field strength up to 14 T. A substantial, nonsaturating magnetoresistance (MR) that reaches 5.15 × 105% at 1.8 K and 9 T obeys a single-parameter scaling, suggesting an effective unified scattering rate across a broad temperature range from 1.8 to 250 K. Importantly, distinct quantum oscillations in the Seebeck coefficient identify multiple extremal orbits with frequencies F = 62.5–1476 T, which are mutually verified by the torque de Haas–van Alphen (dHvA) oscillations and result in small cyclotron masses m* ≈ 0.072–0.16me via Lifshitz–Kosevich analysis. The angular evolution of the dominant frequencies supports three-dimensional multiband pockets/four groups of pockets, and an additional weak branch at F0 ≈ 62.5 T is robust against data-processing variations. Our results establish comprehensive quantum oscillations as a sensitive probe of multiband fermiology and scattering scaling in Dirac semimetals, with implications for understanding the mechanism of extreme MR behavior.