  Single crystals of HoIr$_2$Si$_2$ with the body-centered ThCr$_2$Si$_2$-type
structure ($I4/mmm$) were grown by Bridgman method from indium flux. Single
crystal structure determination yielded a Si-z position of 0.378(1) in the
structure. We excluded the presence of the high temperature phase with the
primitive CaBe$_2$Ge$_2$-type structure ($P 4/n m m$) by powder X-ray
diffraction. Magnetic measurements on the single crystals yield a Neel
temperature of $T_{\rm N}=22\,\rm K$. In the inverse magnetic susceptibility a
strong anisotropy with Weiss temperatures $\Theta_{W}^{001}=26\,\rm K$ and
$\Theta_{W}^{100}=-26\,\rm K$ occurs above $T_{\rm N}$. The effective magnetic
moment $\mu_{\rm eff}^{001}=10.64\mu_{B}$ and $\mu_{\rm
eff}^{100}=10.53\mu_{B}$ is close to the expected value for a free Ho$^{3+}$
ion, $\mu_{\rm eff}^{calc}=10.6\mu_{B}$. The field dependent magnetization
shows a step-like behaviour due to crystalline electric field effects.

Strongly Correlated Electrons