  Time-reversal symmetry (TRS) may be broken in superconductors with three or
more condensates interacting repulsively, yielding two degenerate states
specified by chirality of gap functions. We consider a loop of such
superconductor with two halves occupied by the two states with opposite
chiralities. Fractional flux plateaus are found in magnetization curve
associated with free-energy minima, where the two domain walls between the two
halves accommodate different inter-component phase kinks leading to finite
winding numbers in a part of the whole condensates around the loop. Fractional
flux plateaus form pairs with their heights related to the flux quantum {\Phi}0
= hc/2e. This phenomenon is a clear evidence of time-reversal symmetry broken
(TRSB) superconductivity, which in a general point of view provides a novel
chance to explore relative phase difference, phase kink and soliton in
ubiquitous multi-component superconductivity such as that in iron pnicitides.
