The symmetries of the t=1 and t=0 pair-fields are different. The
consequences for rotational spectra are discussed. For t=1, the concept of
spontaneous breaking and subsequent restoration of the isospin symmetry turns
out to be important. It permits us to describe the proton-neutron
pair-correlation within the conventional frame of pairing between like
particles. The experimental data are consistent with the presence of a t=1
field at low spin in NβZ nuclei. For a substantial t=0 field, the
spectra of even-even and odd-odd NβZ nuclei become similar. The
possibility of a rotationally induced J=1 pair-field at high spin is
considered.Comment: 7 pages 9 figure