On the Phase Boundaries of the Integer Quantum Hall Effect. II

It is shown that the statements about the observation of the transitions between the insulating phase and the integer quantum Hall effect phases with the quantized Hall conductivity ${\sigma }_{xy}^q$ $\ge 3e^2\mathrm{/}h$ made in a number of works are unjustified. In these works, the crossing points of the magnetic field dependences of the diagonal resistivity at different temperatures at ${\omega }_c\tau \approx 1$ have been misidentified as the critical points of the phase transitions. In fact, these crossing points are due to the sign change of the derivative $d{\rho }_{xx}\mathrm{/}dT$ owing to the quantum corrections to the conductivity.