  We report the magnetic properties strongly varying with the rare-earth
elements in the newly found ternary compounds $R$Al$_{0.9}$Si$_{1.1}$, which
crystallize in the tetragonal $\alpha$-ThSi$_2$-type structure. For $R$ = Ce
the alloy has a weak ferromagnetism below 11 K and for $R$ = Pr it orders
ferromagnetically at 17 K, while for $R$ = Gd it is antiferromagnetic with
$T_{\rm N}$ = 30.5 K. In addition, we find no field effect on $T_{\rm N}$ of
$R$ = Gd because of the large internal mean field, but significant changes in
the magnetic properties of $R$ = Ce and Pr.
