Quantum interference in a macroscopic van der Waals conductor

Quantum corrections to charge transport can give rise to an oscillatory magnetoconductance, typically observed in mesoscopic samples with a length shorter than or comparable to the phase coherence length. Here, we report the observation of magnetoconductance oscillations periodic in magnetic field with an amplitude of the order of e²/h in macroscopic samples of highly oriented pyrolytic graphite (HOPG). The observed effect emerges when all carriers are confined to their lowest Landau levels. We argue that this quantum interference phenomenon can be explained by invoking moir\'e superlattices with a discrete distribution in periodicity. According to our results, when the magnetic length B, the Fermi wavelength λF, and the length scale of fluctuations in local chemical potential are comparable in a layered conductor, quantum corrections can be detected over centimetric length scales.