  We present a study of the magnetoresistance of highly oriented pyrolytic
graphite (HOPG) as a function of the sample size. Our results show
unequivocally that the magnetoresistance reduces with the sample size even for
samples of hundreds of micrometers size. This sample size effect is due the
large mean free path and Fermi wavelength of carriers in graphite and may
explain the observed practically absence of magnetoresistance in micrometer
confined small graphene samples where quantum effects should be at hand. These
were not taken into account in the literature yet and ask for a revision of
experimental and theoretical work on graphite.
