  Detailed structural and magnetotransport properties of the monophosphate
tungsten bronze K$_{x}$P$_4$W$_{8}$O$_{32}$ single crystals are reported. Both
galvanomagnetic and thermal properties are shown to be consistent with a charge
density wave electronic transition due to hidden nesting of quasi - 1D portion
of the Fermi surface. We also observe the enhancement of electronic anisotropy
due to reconstruction of the Fermi surface at the Peierls transition. The
resistivity presents a thermal hysteresis suggesting a first order nature
characteristics of a strong coupling scenario. However, other measurements such
as the change of carriers density demonstrate a second order Peierls scenario
with weak coupling features. We suggest that the structural transition driven
by the residual strain in the K - P - O environment is responsible for the
resistivity hysteresis and modifes the Fermi surface which then helps the rise
to the second order Peierls instability.
