  The results of experimental study of the magnetoconductivity of 2D electron
gas caused by suppression of the interference quantum correction in HgTe single
quantum well heterostructure with the inverted energy spectrum are presented.
It is shown that only the antilocalization magnetoconductivity is observed at
the relatively high conductivity $\sigma>(20-30)G_0$, where $G_0=
e^2/2\pi^2\hbar$. The antilocalization correction demonstrates a crossover from
$0.5\ln{(\tau_\phi/\tau)}$ to $1.0\ln{(\tau_\phi/\tau)}$ behavior with the
increasing conductivity or decreasing temperature (here $\tau_\phi$ and $\tau$
are the phase relaxation and transport relaxation times, respectively). It is
interpreted as a result of crossover to the regime when the two chiral branches
of the electron energy spectrum contribute to the weak antilocalization
independently. At lower conductivity $\sigma<(20-30)G_0$, the
magnetoconductivity behaves itself analogously to that in usual 2D systems with
the fast spin relaxation: being negative in low magnetic field it becomes
positive in higher one. We have found that the temperature dependences of the
fitting parameter $\tau_\phi$ corresponding to the phase relaxation time
demonstrate reasonable behavior, close to 1/T, over the whole conductivity
range from $5G_0$ up to $130G_0$. However, the $\tau_\phi$ value remains
practically independent of the conductivity in distinction to the conventional
2D systems with the simple energy spectrum, in which $\tau_\phi$ is enhanced
with the conductivity.
