  We have found a new mean field solution in the BCS theory of
superconductivity. This unconventional solution indicates the existence of
superconducting phase transitions of third order in thin films, or in bulk
matter with a layered structure. The critical temperature increases with
decreasing thickness of the layer, and does not exhibit the isotope effect. The
electronic specific heat is a continuous function of temperature with a
discontinuity in its derivative.
