  We investigate low-temperature magneto-transport in recently developed,
high-quality multi-terminal suspended bilayer graphene devices, enabling the
independent measurement of the longitudinal and transverse resistance. We
observe clear signatures of the fractional quantum Hall effect, with different
states that are either fully developed, and exhibit a clear plateau in the
transverse resistance with a concomitant dip in longitudinal resistance, or
incipient, and exhibit only a longitudinal resistance minimum. All observed
states scale as a function of filling factor nu, as expected. An unprecedented
even-denominator fractional state is observed at nu = -1/2 on the hole side,
exhibiting a clear plateau in Rxy quantized at the expected value of 2h/e^2
with a precision of ~0.5%. Many of our observations, together with a recent
electronic compressibility measurement performed in graphene bilayers on
hexagonal boron-nitride (hBN) substrates, are consistent with a recent theory
that accounts for the effect of the degeneracy between the N=0 and N=1 Landau
levels in the fractional quantum Hall effect, and predicts the occurrence of a
Moore-Read type nu = -1/2 state. Owing to the experimental flexibility of
bilayer graphene --which has a gate-dependent band structure, can be easily
accessed by scanning probes, and can be contacted with materials such as
superconductors--, our findings offer new possibilities to explore the
microscopic nature of even-denominator fractional quantum Hall effect.
