  It is presented a theory that describes a spin glass phase at finite
temperatures in Kondo lattice systems with an additional RKKY interaction
represented by long range, random couplings among localized spins like in the
Sherrington- Kirkpatrick (SK) spin glass model. The problem is studied within
the functional integral formalism where the spin operators are represented by
bilinear combinations of fermionic (anticommuting) Grassmann variables. The
Kondo and spin glass transitions are both described with the mean field like
static ansatz that reproduces good results in the two well known limits. At
high temperatures and low values of the Kondo coupling there is a paramagnetic
(disordered) phase with vanishing Kondo and spin glass order parameters. By
lowering the temperature a second order transition line is found at Tsg to a
spin glass phase. For larger values of the Kondo coupling there is a second
order transition line at roughly Tk to a Kondo ordered state. For T<Tsg the
transition between the Kondo and spin glass phases becomes first order.
