  We present a Brownian dynamics study of a 2d bath of active particles
interacting among each other through usual steric interactions and,
additionally, via non-reciprocal avoidant orientational interactions. We
motivate them by the fact that the two flagella of the alga Chlamydomonas
interact sterically with nearby surfaces such that a torque acts on the alga.
As expected, in most cases such interactions disrupt the motility-induced
particle clustering in active baths. Surprisingly, however, we find that the
active particles can self-organize into collectively moving flocks if the range
of non-reciprocal interactions is close to that of steric interactions. We
observe that the flocking motion can manifest itself through a variety of
structural forms, spanning from single dense bands to multiple moderately-dense
stripes, which are highly dynamic. The flocking order parameter is found to be
only weakly dependent on the underlying flock structure. Together with the
variance of the local-density distribution, one can clearly group the flocking
motion into the two separate band and dynamic-stripes states.
