  We study the competition between alpha-type and conventional pair
condensation in the ground state of nuclei with neutrons and protons
interacting via a charge-independent pairing interaction. The ground state is
described by a product of two condensates, one of alpha-like quartets and the
other one of pairs in excess relative to the isotope with N=Z. It is shown that
this ansatz for the ground state gives very accurate pairing correlation
energies for nuclei with the valence nucleons above the closed cores 16O, 40Ca
and 100Sn. These results indicate that alpha-type correlations are important
not only for the self-conjugate nuclei but also for nuclei away of N=Z line. In
the latter case alpha-like quartets coexist with the collective Cooper pairs
formed by the nucleons in excess.
