  We investigate the origin of the high Neel temperature recently found in Tc
perovskites. The electronic structure in the magnetic state of SrTcO3 and its
3d analogue SrMnO3 is calculated within a framework combining band-structure
and many-body methods. In agreement with experiment, the Neel temperature of
SrTcO3 is found to be four times larger than that of SrMnO3. We show that this
is because the Tc-compound lies on the verge of the itinerant-to-localized
transition, and also has a larger bandwidth, while the Mn-compound lies deeper
into the localized side. For SrTcO3 we predict that the Neel temperature
depends weakly on applied pressure, in clear violation of Bloch's rule,
signaling the complete breakdown of the localized picture.
