  The mechanism explaining the key role of AFM correlations in formation of the
heavy fermion state is offered. It is shown that in the case of $(T^*-T_N)/T_N
<< 1$ the critical spin fluctuations transform the mean-field second-order
transition to RVB state into the crossover from high-temperature paramagnetic
behavior of localized spins to strongly correlated spin liquid with quasi
itinerant character of susceptibility. Thus the spin liquid state {\it by its
origin} is close to magnetic instability, so either short-range or long-range
AFM order should arise at low T.
