Ultracold Heteronuclear Fermi-Fermi Molecules

We report on the first creation of ultracold bosonic heteronuclear molecules of two fermionic species, (6)Li and (40)K, 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.