  We present the two-loop renormalization group (RG) calculations of all the
susceptibilities associated with the two-dimensional flat Fermi surface with
rounded corners (FS). Our approach follows our fermionic field theory RG method
presented in detail earlier on. In one loop order our calculation reproduce the
results obtained previously by other RG schemes. All susceptibilities diverge
at some energy scale and the antiferromagnetic SDW correlations produce indeed
the dominant instability in the physical system. In contrast, in two-loop
order, for a given initial set of values of coupling constant regime only one
of the susceptibilities at a time seems to diverge.
