  Observing spontaneous velocity ordering or flocking during motility induced
phase separation (MIPS) in a system of spherical active Brownian particles
without alignment interaction is challenging. We take up this problem by
performing simulations of spherical active inertial particles with purely
repulsive potential in presence of thermal noise and absence of any explicit
alignment interaction. Our results not only show the presence of MIPS, but also
reveal a micro-flocking transition. We characterize this transition in terms of
a velocity order parameter as well as a characteristic length scale derived
from the spatial correlation of the velocities.
