  The field and temperature dependencies of the longitudinal and Hall
resistivity have been measured for FeSe${}_{1-x}$S${}_{x}$ (x=0.04, 0.09 and
0.19) single crystals. The sample FeSe${}_{0.81}$S${}_{0.19}$ does not show a
transition to an orthorhombic phase and exhibits at low temperatures the
transport properties quite different from those of orthorhombic samples. The
behavior of FeSe${}_{0.81}$S${}_{0.19}$ is well described by the simple two
band model with comparable values of hole and electron mobility. In particular,
at low temperatures the transverse resistance shows a linear field dependence,
the magnetoresistance follow a quadratic field dependence and obeys to Kohler's
rule. In contrast, Kohler's rule is strongly violated for samples having an
orthorhombic low temperature structure. However, the transport properties of
the orthorhombic samples can be satisfactory described by the three band model
with the pair of almost equivalent to the tetragonal sample hole and electron
bands, supplemented with the highly mobile electron band which has two order
smaller carrier number. Therefore, the peculiarity of the low temperature
transport properties of the orthorhombic Fe(SeS) samples, as probably of many
other orthorhombic iron superconductors, is due to the presence of a small
number of highly mobile carriers which originate from the local regions of the
Fermi surface, presumably, nearby the Van Hove singularity points.
