  In a recent paper by Link, it was pointed out that the the standard picture
of the neutron star core, composed of a mixture of a neutron superfluid and a
proton type-II superconductor, is inconsistent with observations of long period
precession in isolated pulsars. In the following we will show that intervortex
force between the magnetic flux tubes may be attractive resulting in a type-I
(rather than type-II) superconductor. In this case the magnetic field cannot
exist in the form of magnetic flux tubes, supporting Link's observation. This
behavior of the system is due to the strong interaction between the
proton-neutron Cooper pairs, which was previously ignored. We also calculate
the critical magnetic fields H_c and H_c2 for type-I/II superconductors. These
results also support our claim of type-I superconductivity in the cores of
neutron stars.
