  We have discovered a new nontrivial aspect of electronic topological
transition (ETT) in a 2D free fermion system on a square lattice. The
corresponding exotic quantum critical point, \delta=\delta_c, T=0, (n=1-\delta
is an electron concentration) is at the origin of anomalous behaviour in the
interacting system on one side of ETT, \delta<\delta_c. The most important is
an appearance of the line of characteristic temperatures, T^*(\delta) \propto
\delta_c-\delta. Application of the theory to high-T_c cuprates reveals a
striking similarity to the observed experimentally behaviour in the underdoped
regime (NMR and ARPES).
