  57Fe-M\"ossbauer studies of superconducting Rb0.8Fe1.6Se2.0 with TC = 32.4 K
were performed on single-crystalline and polycrystalline samples in the
temperature range 4.2 K to 295 K. They reveal the presence of 88% magnetic and
12% non-magnetic Fe2+ species with the same polarization dependence of their
hyperfine spectra. The magnetic species are attributed to the 16i sites of the
\surd5 x \surd5 x 1 superstructure, and non-magnetic species to a nano-sized
phase postulated from recent studies of superconducting KxFe2-ySe2 systems. The
57Fe-spectrum of a single-crystalline sample in an external field of 50 kOe
applied parallel to the crystallographic c-axis confirms the antiferromagnetic
order between fourfold ferromagnetic Fe(16i) supermoments. The results are
discussed with respect to the coexistence of superconductivity and magnetism as
well as nano-scale phase separation in AxFe2-ySe2 systems.
