  We report on far infrared magneto-transmission measurements on a thin
graphite sample prepared by exfoliation of highly oriented pyrolytic graphite.
In magnetic field, absorption lines exhibiting a blue-shift proportional to
sqrtB are observed. This is a fingerprint for massless Dirac holes at the H
point in bulk graphite. The Fermi velocity is found to be c*=1.02x10^6 m/s and
the pseudogap at the H point is estimated to be below 10 meV. Although the
holes behave to a first approximation as a strictly 2D gas of Dirac fermions,
the full 3D band structure has to be taken into account to explain all the
observed spectral features.
