  We report on the first creation of ultracold bosonic heteronuclear molecules
of two fermionic species, 6Li and 40K, by a magnetic field sweep across an
interspecies s-wave Feshbach resonance. This allows us to associate up to
4x10^4 molecules with high efficiencies of up to 50%. Using direct imaging of
the molecules, we measure increased lifetimes of the molecules close to
resonance of more than 100 ms in the molecule-atom mixture stored in a harmonic
trap.
