  We study static properties of attractively interacting Bose-Fermi mixtures of
uniform atomic gases at zero temperature. Using Green's function formalism we
calculate boson-fermion scattering amplitude and fermion self-energy in the
medium to lowest order of the hole line expansion. We study ground state energy
and pressure as functions of the scattering length for a few values of the
boson-fermion mass ratio $m_b/m_f$ and the number ratio $N_b/N_f$. We find that
the attractive contribution to energy is greatly enhanced for small values of
the mass ratio. We study the role of the Bose-Fermi pair correlations in the
mixture by calculating the pole of the boson-fermion scattering amplitude in
the medium. The pole shows a standard quasiparticle dispersion for a Bose-Fermi
pair, for $m_b/m_f\geq 1$. For small values of the mass ratio, on the other
hand, a Bose-Fermi pair with a finite center-of-mass momentum experiences a
strong attraction, implying large medium effects. In addition, we also study
the fermion dispersion relation. We find two dispersion branches with the
possibility of the avoided crossings. This strongly depends on the number rario
$N_b/N_f$.
