  In this study, we conducted various magnetotransport measurements on
Fe$_{1+y}$Te$_{1-x}$Se$_{x}$ single crystals from which excess iron was
sufficiently removed. Our results revealed that crossover from the incoherent
to the coherent electronic state and opening of the pseudogap occur at high
temperatures ($\approx$ 150 K for $x$ = 0.2). This is accompanied by a more
substantial pseudogap and the emergence of a phase with a multi-band nature at
lower temperatures (below $\approx$ 50 K for $x$ = 0.2) before
superconductivity sets in. A comparison of these results with those of the
as-grown (non-superconducting) samples implies that the coherent state
accompanied by the pseudogap is needed for the occurrence of superconductivity
in this system.
