  Thermodynamic properties of the four-dimensional cross-polytope model, the
16-cell model, which is an example of higher dimensional generalizations of the
octahedron model, are studied on the square lattice. By means of the corner
transfer matrix renormalization group (CTMRG) method, presence of the
first-order phase transition is confirmed. The latent heat is estimated to be
$L_4^{~} = 0.3172$, which is larger than that of the octahedron model $L_3^{~}
= 0.0516$. The result suggests that the latent heat increases with the internal
dimension $n$ when the higher-dimensional series of the cross-polytope models
is considered.
