  In the following paper we investigate the critical temperature $T_c$ behavior
in the two-dimensional S/TI (S denotes superconductor and TI - topological
insulator) junction with a proximity induced in-plane helical magnetization in
the TI surface. The calculations of $T_c$ are performed using the general
self-consistent approach based on the Usadel equations in Matsubara Green's
functions technique. We show that the presence of the helical magnetization
leads to the nonmonotonic behavior of the critical temperature as a function of
the topological insulator layer thickness.
