A study of the t-t'-U model in the antiferromagnetic phase by
means of the *COM* is reported in
Ref. [87]. In particular the following
properties have been computed:

- The thermodynamic properties (i.e., critical interaction, order
parameter: staggered magnetization, internal energy)
[87]
- The single-particle properties (i.e., energy spectra) [87]

The *COM* results have been analyzed in relation with
the ones obtained by:

We provided simultaneously a fully self-consistent treatment of
the paramagnetic and the antiferromagnetic phase. Near half
filling the critical value of the Coulomb repulsion as a function
of
and the temperature dependence of the
magnetization and internal energy have been studied. turns
out to be significantly larger than what obtained by
renormalization group techniques
[88,89]. This might be due to
the fact, that the latter is valid only in the weak coupling
limit, whereas *COM* provides a good approximation for
any value of the interaction. The band structure shows the opening
of a gap at the transition line between the paramagnetic and the
antiferromagnetic phase. With decreasing magnetization the energy
increases and reaches the paramagnetic value at vanishing
magnetization.