  An analysis of the slab phase as it is expected in the innermost layer of
neutron-star crusts is performed within the Hartree-Fock-Bogoliubov framework.
We take the periodicity of the slabs into account using Bloch boundary
conditions, in order to well describe the interplay between the band structure
and superfluidity. We introduce a relative flow between the slabs and the
surrounding neutron gas in a time-independent way. This induces a non-trivial
phase of the complex order parameter, leading to a counterflow between neutrons
inside and outside the slabs. With the resulting current, we compute the actual
neutron superfluid fraction. For the latter our results are slightly larger
than previous ones obtained in normal band theory, suggesting that normal band
theory overestimates the entrainment effect.
