  Composite fermions in fractional quantum Hall (FQH) systems are believed to
form a Fermi sea of weakly interacting particles at half filling $\nu=1/2$.
Recently, it was proposed (D. T. Son, Phys. Rev. X 5, 031027 (2015)) that these
composite fermions are Dirac particles. In our work, we demonstrate
experimentally that composite fermions found in monolayer graphene are Dirac
particles at half filling. Our experiments have addressed FQH states in
high-mobility, suspended graphene Corbino disks in the vicinity of $\nu=1/2$.
We find strong temperature dependence of conductivity $\sigma$ away from half
filling, which is consistent with the expected electron-electron interaction
induced gaps in the FQH state. At half filling, however, the temperature
dependence of conductivity $\sigma(T)$ becomes quite weak as expected for a
Fermi sea of composite fermions and we find only logarithmic dependence of
$\sigma$ on $T$. The sign of this quantum correction coincides with weak
antilocalization of composite fermions, which reveals the relativistic Dirac
nature of composite fermions in graphene.
