  We report on the investigation of magnetic field induced charge density wave
and Hall coefficient sign reversal in a quasi-two dimensional electronic system
of highly oriented pyrolytic graphite under very strong magnetic field. The
change of Hall sign coefficient from negative to positive occurs at low
temperature and high magnetic field just after the charge density wave
transition, suggesting the role of hole-like quasi-particles in this effect.
Angular dependent measurements show that the charge density wave transition and
Hall sign reversal fields follow the magnetic field component along the c-axis
of graphite.
