  The dynamical evolution of a two-site Hubbard model is derived in the
presence of an uniform external magnetic field for a general initial state. The
time evolution of the half-filled (two-particle) case has a complex behaviour.
Under certain initial conditions, the average number of fermions in
one-particle state, in the half-filled case, is not necessarily periodic, even
though the magnetization remains periodic. The results obtained may be applied
to study the magnetization and the transition dipole moment of the organic
charge-transfer salts in the in-phase mode.
