  The strong Coulomb interaction between massless Dirac fermions can drive a
semimetal-insulator transition in single-layer graphene by dynamically
generating an excitonic fermion gap. There is a critical interaction strength
$\lambda_c$ that separates the semimetal phase from the insulator phase. We
calculate the specific heat and susceptibility of the system and show that they
exhibit distinct behaviors in the semimetal and insulator phases.
