Spectral analysis of Shubnikov de Haas (SdH) oscillations of magnetoresistance and of Quantum Hall Effect (QHE) measured in quasi-2D highly oriented pyrolytic graphite (HOPG) [Phys. Rev. Lett. 90, 156402 (2003)] reveals two types of carriers: normal (massive) electrons with Berry phase 0 and Dirac-like (massless) holes with Berry phase pi. We demonstrate that recently reported integer- and semi-integer QHE for bi-layer and single-layer graphenes take place simultaneously in HOPG samples.
@article{arxiv.cond-mat/0609037,
title = {Dirac and Normal Fermions in Graphite and Graphene: Implications to the Quantum Hall Effect},
author = {Igor A. Luk'yanchuk and Yakov Kopelevich},
journal= {arXiv preprint arXiv:cond-mat/0609037},
year = {2007}
}