  The synthesis, crystal structure, and physical properties studied by means of
x-ray diffraction, magnetic, thermal and transport measurements of
CeMAl$_{4}$Si$_{2}$ (M = Rh, Ir, Pt) are reported, along with the electronic
structure calculations for LaMAl$_{4}$Si$_{2}$ (M = Rh, Ir, Pt). These
materials adopt a tetragonal crystal structure (space group P4/mmm) comprised
of BaAl$_4$ blocks, separated by MAl$_2$ units, stacked along the $c$-axis.
Both CeRhAl$_{4}$Si$_{2}$ and CeIrAl$_{4}$Si$_{2}$ order antiferromagnetically
below $T_{N1}$=14 and 16 K, respectively, and undergo a second
antiferromagnetic transitition at lower temperature ($T_{N2}$=9 and 14 K,
respectively). CePtAl$_{4}$Si$_{2}$ orders ferromagnetically below $T_C$ =3 K
with an ordered moment of $\mu_{sat}$=0.8 $\mu_{B}$ for a magnetic field
applied perpendicular to the $c$-axis. Electronic structure calculations reveal
quasi-2D character of the Fermi surface.
