A layered superconductor is studied in the presence of a magnetic field along the layers. With the help of a transformation to a Coulomb-gas representation it is shown that even in the limit of high field the phase transition into the phase with effectively decoupled layers is impossible. Contrary to the suggestion by Efetov [Sov. Phys. JETP 49, 905 (1979)] the coherence between the layers will be lost simultaneously with the total destruction of superconductivity.

• Received 24 February 1992

DOI:https://doi.org/10.1103/PhysRevB.46.6395