  We explore the transport properties of an interacting Fermi gas in a
three-dimensional optical lattice. The center of mass dynamics of the atoms
after a sudden displacement of the trap minimum is monitored for different
interaction strengths and lattice fillings. With increasingly strong attractive
interactions the weakly damped oscillation, observed for the non-interacting
case, turns into a slow relaxational drift. Tuning the interaction strength
during the evolution allows us to dynamically control the transport behavior.
Strong attraction between the atoms leads to the formation of local pairs with
a reduced tunneling rate. The interpretation in terms of pair formation is
supported by a measurement of the number of doubly occupied lattice sites. This
quantity also allows us to determine the temperature of the non-interacting gas
in the lattice to be as low as (27\pm2)% of the Fermi temperature.
