  The magnetization process of the spin-1/2 antiferromagnetic Heisenberg model
on two-dimensional square-kagome lattice is studied theoretically. The
metamagnetic jumps exist in the magnetization process at the higher edge of the
1/3 and 2/3 plateaus. The parameter-dependencies of the critical field and the
magnitude of the magnetization jump at the higher edge of the 1/3 plateau are
obtained by using the approximated state in the unit cell and compared with the
nu- merical results of the exact diagonalization of 42 sites.
