  Nonreciprocal current responses arise in a broad range of systems, from
magnons and phonons to supercurrents, due to an interplay between spatial and
temporal symmetry breakings. These find applications in devices, such as
circulators and rectifiers, as well as in probing the interactions and states
that underlie the nonreciprocity. An established symmetry argument anticipates
emergence of nonreciprocal currents along a direction perpendicular to the
applied magnetic field that breaks the time-reversal symmetry. Here, motivated
by recent experiments, we examine the emergence of nonreciprocity in
vortex-limited superconducting critical currents along an applied magnetic
field. Employing London's equations for describing the Meissner response of a
superconducting film, we find that an additional symmetry breaking due to a
preferred vortex axis enables nonreciprocal critical currents along the applied
magnetic field, consistent with the so far unexplained experimental
observation. Building on our concrete theoretical model for supercurrents, we
discuss a possible generalization of the prevailing symmetry consideration to
encompass nonreciprocal currents along the time-reversal symmetry breaking
direction.
