  A single-crystal sample of a DO3-ordered Fe3Si compound was studied by means
of the 57Fe M\"ossbauer spectroscopy. Spectra have been recorded in a
transmission geometry in the temperature range between 5 and 850 K. They have
been analyzed either in terms of five sextets or five hyperfine field
distribution curves. Concerning the former three sub spectra have been
attributed to Fe atoms occupying the B sites and having 8Fe, 7Fe1Si and 6Fe2Si
atoms in the first coordination shell (1NN), respectively, and two have been
attributed to Fe atoms residing on the A and C sites and having 4Fe4Si and
3Fe5Si atoms in the 1NN, respectively. Based on the temperature dependence of
the center shifts values the Debye temperature, T_D, have been determined. TD
was found to be equal to 491 (11) K for the sites A and C, and to 403 (3) K the
site B. The smaller value of T_D coincides with the smaller values of the
hyperfine field, H. Changes in H caused by one Si atom present in the 1NN have
been determined as ca.13 kOe for Fe atoms occupying the A and C sites and ca.54
kOe for Fe atoms present on the B sites. These changes have been also expressed
in terms of the underlying number of polarized s-like electrons, dNs. For the
Fe atoms situated on the A and C sites dNs=0.03 was found while for those
occupying the B sites dNs=0.17.
