  In the Minimal Supersymmetric Model (MSSM) the hitherto unconstrained flavor
mixing between top-squark and charm-squark will induce the flavor-changing
neutral-current (FCNC) interaction between top quark and charm quark, which
then give rise to various processes at the next generation linear collider
(NLC), i.e., the top-charm associated productions via $e^+ e^-$, $e^- \gamma$
and $\gamma \gamma$ collisions as well as the top quark rare decays $t \to c V$
($V=g$, $\gamma $ or $Z$). All these processes involve the same part of the
parameter space of the MSSM. Through a comparative analysis for all these
processes at the NLC, we found the best channel to probe such SUSY-induced top
quark FCNC is the top-charm associated production in $\gamma \gamma$ collision,
which occurs at a much higher rate than $e^+ e^-$ or $e^- \gamma$ collision and
may reach the detectable level for some part of the parameter space. Since the
rates predicted by the Standard Model are far below the detectable level, the
observation of such FCNC events would be a robust indirect evidence of SUSY.
