  We consider fundamental facts from the theory of Hopf superalgebras. We use
them to construct the quantum double of the quantum superalgebra $sl(2|1)$ at
roots of unity. Thus we obtain a multiplicative formula for universal
$R$-matrix. Next we construct an $R$-matrix to investigate parametrized family
of centralizer algebras. We give multiplication laws in particular case and
describe a structure of such algebras in the general case.
