  We investigate direct above-threshold ionization in diatomic molecules, with
particular emphasis on how quantum interference is altered by a driving field
of non-vanishing ellipticity. This interference may be either temporal, i.e.,
related to ionization events occurring at different times, or spatial, i.e.,
related to the electron emission at different centers in the molecule.
Employing the strong-field approximation and saddle-point methods, we find
that, in general, for non-vanishing ellipticity, there will be a blurring of
the temporal and spatial interference patterns. The former blurring is caused
by the electron velocity component perpendicular to the major polarization
axis, while spatial interference is washed out as a consequence either of s-p
mixing, or of the temporal dependence of the ionization prefactor. Both types
of interference are analyzed in detail in terms of electron trajectories, and
specific conditions for which sharp fringes occur are provided.
