  We consider the Sherrington-Kirkpatrick model and we prove that the
thermodynamic limit of the quenched free energy per site is strictly greater
than the corresponding replica symmetric approximation, for all values of the
temperature and of the magnetic field below the Almeida-Thouless line. This is
based on recent rigorous bounds by F. Guerra, relating the true free energy of
the system to the Parisi solution with replica symmetry breaking.
