  It has been shown within the Landauer single-channel approach that the
presence of the 0.7 anomaly in the conductance of a ballistic microcontact and
the respective plateau in the thermopower implies unusual pinning of the
potential barrier height $U$ at a depth of $k_BT$ below the Fermi level $E_F$.
A simple way of taking into account the effect of electron-electron interaction
on the profile and temperature dependence of a smooth one-dimensional potential
barrier in the lower spin degeneracy subband of the microcontact has been
proposed. The calculated temperature dependences of the conductance and Seebeck
coefficient agree with the experimental gate-voltage dependences, including the
emergence of anomalous plateaux with an increase in temperature.
