  We present a theory which is able to explain enhanced magnetic
quantum-oscillation amplitudes in the superconducting state of a layered metal
with incoherent electronic transport across the layers. The incoherence acts
through the deformation of the layer-stacking factor which becomes complex and
decreases the total scattering rate in the mixed state. This novel mechanism
can compensate the usual decrease of the Dingle factor below the upper critical
magnetic field caused by the intralayer scattering.
