  We investigate the possibility of forming Li+Yb ultracold molecules by
magnetoassociation in mixtures of ultracold atoms. We find that magnetically
tunable Feshbach resonances exist, but are extremely narrow for even-mass
ytterbium isotopes, which all have zero spin. For odd-mass Yb isotopes,
however, there is a new mechanism due to hyperfine coupling between the
electron spin and the Yb nuclear magnetic moment. This mechanism produces
Feshbach resonances for fermionic Yb isotopes that can be more than 2 orders of
magnitude larger than for the bosonic counterparts.
