  Superconducting FeSe has been investigated by measurements of the magnetic
susceptibility versus temperature and Moessbauer spectroscopy at various
temperatures including strong external magnetic fields applied to the absorber.
It was found that isomer shift exhibits sharply defined increase at about 105 K
leading to the lowering of the electron density on iron nucleus by 0.02
electron/a.u.^3. Above jump in the electron density is correlated with the
transition from the P4/nmm to the Cmma structure, while decreasing temperature.
Moessbauer measurements in the external magnetic field and for temperatures
below transition to the superconducting state revealed null magnetic moment on
iron atoms. Hence, the compound exhibits either Pauli paramagnetism or
diamagnetic behavior. The principal component of the electric field gradient on
the iron nucleus was found as negative on the iron site.
