Approaching three-dimensional quantum Hall effect in bulk HfTe5

We report the electronic transport features of HfTe5 under external magnetic field. We observe a series of plateaus in Hall resistance rho(xy) as magnetic field increases until it reaches the quantum limit at 1-2 Tesla. At the plateau regions, the longitudinal resistance rho(xx) exhibits local minima Although rho(xx) is still nonzero, its value becomes much smaller than rho(xy) at the last few plateaus. By mapping the Fermi surface via measuring the Shubonikov-de Haas oscillation, we find that the strength of Hall plateau is proportional to the Fermi wavelength, suggesting that its formation may be attributed to the gap opening from the interaction driven Fermi surface instability. By comparing the bulk band structures of ZrTe5 and HfTe5, we find that there exists an extra pocket near the Fermi level of HfTe5, which may lead to the finite but nonzero longitudinal conductance.