  The quantum Hall (QH) effect in two-dimensional (2D) electrons and holes in
high quality graphene samples is studied in strong magnetic fields up to 45 T.
QH plateaus at filling factors $\nu=0,\pm 1,\pm 4$ are discovered at magnetic
fields $B>$20 T, indicating the lifting of the four-fold degeneracy of the
previously observed QH states at $\nu=\pm(|n|+1/2)$, where $n$ is the Landau
level index. In particular, the presence of the $\nu=0, \pm 1$ QH plateaus
indicates that the Landau level at the charge neutral Dirac point splits into
four sublevels, lifting sublattice and spin degeneracy. The QH effect at
$\nu=\pm 4$ is investigated in tilted magnetic field and can be attributed to
lifting of the spin-degeneracy of the $n=1$ Landau level.

Mesoscale and Nanoscale Physics;Strongly Correlated Electrons