Fig. 2: Thickness dependence of oscillation period and Fermi surface topology.

a, b The oscillatory component of Sondheimer oscillations (SO) in the longitudinal and transverse resistivity for the 12.6 μm sample, respectively. As the field increases, the amplitude of oscillation grows. c, d The oscillatory component of SO in the longitudinal and transverse resistivity for the 475 μm sample, respectively. e Oscillation period, ΔB, as a function of thickness, d. The solid line represents a linear variation with a slope corresponding to ΔB ⋅ d = 58 T ⋅ μm. The data point reported by Grenier et al.⁸ for a 1.02 mm thick sample is also included. Inserting this ΔBd in Equation (2) yields \(\frac{\partial A}{\partial {k}_{z}}=8.76\) Å⁻¹. f The computed cross section of A for the `lens-shaped' electron-like pocket as a function of k_z shown near the southern pole²⁹. This pocket, as shown in the inset, is not elliptical. The plot of A vs. k_z is perfectly linear, and its slope yields \(\frac{\partial A}{\partial {k}_{z}}=\pm 8.73\) Å⁻¹. This corresponds within a margin less than a percent to the experimentally derived \(\frac{\partial A}{\partial {k}_{z}}\). The linear out-of-plane dispersion of this band, which hosts semi-Dirac fermions, is the origin of the constant \(\frac{\partial A}{\partial {k}_{z}}\) over a k_z interval of at least 0.014 Å⁻¹.