  We demonstrate a reversible conversion of a Li2 molecular Bose-Einstein
condensate to a degenerate Fermi gas of atoms by adiabatically crossing a
Feshbach resonance. By optical in situ imaging, we observe a smooth change of
the cloud size in the crossover regime. On the Feshbach resonance, the ensemble
is strongly interacting and the measured cloud size is 75(7)% of the one of a
non-interacting zero-temperature Fermi gas. The high condensate fraction of
more than 90% and the adiabatic crossover suggest our Fermi gas to be cold
enough to form a superfluid.
