Searching for the Fractional Quantum Hall Effect in Graphite

Measurements of basal plane longitudinal ${\rho }_b(B)$ and Hall ${\rho }_H(B)$ resistivities were performed on highly oriented pyrolytic graphite samples in a pulsed magnetic field up to $B=50\mathrm{T}$ applied perpendicular to graphene planes, and temperatures $1.5\mathrm{K}\le T\le 4.2\mathrm{K}$. At $B>30\mathrm{T}$ and for all studied samples, we observed a sign change in ${\rho }_H(B)$ from electron- to holelike. For our best quality sample, the measurements revealed the enhancement in ${\rho }_b(B)$ for $B>34\mathrm{T}$ ($T=1.8\mathrm{K}$), presumably associated with the field-driven charge density wave or Wigner crystallization transition. In addition, well-defined plateaus in ${\rho }_H(B)$ were detected in the ultraquantum limit revealing possible signatures of the fractional quantum Hall effect in graphite.