  The nematic phase transition in electronic liquids, driven by Coulomb
interactions, represents a new class of strongly correlated electronic ground
states. We studied suspended samples of bilayer graphene, annealed so that it
achieves very high quasiparticle mobilities. Bilayer graphene is a truly
two-dimensional material with complex chiral electronic spectra and the high
quality of our samples allowed us to observe strong spectrum reconstructions
and electron topological transitions that can be attributed to a nematic phase
transition and a decrease in rotational symmetry. These results are especially
surprising because no interaction effects have been observed so far in bilayer
graphene in the absence of an applied magnetic field.
