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Quantum oscillations and stacked quantum Hall effect in HfTe5

We report the magneto-transport measurements on bulk HfTe5 with carrier mobility exceeding 100 000 cm2/(V s). The longitudinal resistance anomaly and the sign change in Hall coefficient with temperature are observed, which may be induced by Lifshitz transition. When the magnetic field is applied along the b-axis and a-axis at low temperature, a series of Shubnikov–de Haas oscillations on the longitudinal transport exhibit, demonstrating a three-dimensional Fermi-surface pocket for HfTe5 rather than two-dimensional (2D). The investigations on Landau level fan diagram confirm the existence of the non-trivial π Berry phase. The cyclotron mass [Formula: see text] as around [Formula: see text] and quantum scattering time τ at about 1.76 ps are also estimated with Lifshitz–Kosevich theory. Further detailed analysis suggests that a stacked quantum Hall effect attributed to multi-parallel 2D conduction layers develops in HfTe5.