  Based on low temperature resistivity, heat capacity and magnetization
investigations we show that the unusually strong suppression of
superconductivity in Lu$_x$Zr$_{1-x}$B$_{12}$ BSC-type superconductors in the
range $x$$<$0.08 is caused by the emergence of static spin polarization in the
vicinity of non-magnetic lutetium impurities. The analysis of received results
points to a formation of static magnetic moments with
$\mu_{eff}$$\approx$$3\mu_B$ per Lu-ion. The size of these spin polarized
nanodomains was estimated to be about 5 ${\AA}$.
