  The magnetoresistance (MR) $\Delta \rho/\rho$ of cage-glass compound
Ho$_x$Lu$_{1-x}$B$_{12}$ with various concentration of magnetic holmium ions
($x$$\leq$0.5) has been studied in detail concurrently with magnetization M(T)
and Hall effect investigations on high quality single crystals at temperatures
1.9-120 K and in magnetic field up to 80 kOe. The undertaken analysis of
$\Delta\rho/\rho$ allows us to conclude that the large negative
magnetoresistance (nMR) observed in vicinity of Neel temperature is caused by
scattering of charge carriers on magnetic clusters of Ho$^{3+}$ ions, and that
these nanosize regions with AF exchange inside may be considered as short range
order AF domains. It was shown that the Yosida relation $-\Delta
\rho/\rho$$\sim$$M^2$ provides an adequate description of the nMR effect for
the case of Langevin type behavior of magnetization. Moreover, a reduction of
Ho-ion effective magnetic moments in the range 3-9$\mu_B$ was found to develop
both with temperature lowering and under the increase of holmium content. A
phenomenological description of the large positive quadratic contribution
$\Delta \rho/\rho$$\sim$$\mu_D^2 H^2$ which dominates in
Ho$_x$Lu$_{1-x}$B$_{12}$ in the intermediate temperature range 20-120 K allows
to estimate the drift mobility exponential changes $\mu_D$$\sim$$T^{-a}$ with
$a$=1.3-1.6 depending on Ho concentration. An even more comprehensive behavior
of magnetoresistance has been found in the AF state of Ho$_x$Lu$_{1-x}$B$_{12}$
where an additional linear positive component was observed and attributed to
charge carriers scattering on the spin density wave (SDW). High precision
measurements of $\Delta\rho/\rho=f(H,T)$ have allowed us also to reconstruct
the magnetic H-T phase diagram of Ho$_{0.5}$Lu$_{0.5}$B$_{12}$ and to resolve
its magnetic structure as a superposition of 4f (based on localized moments)
and 5d (based on SDW) components.
