  A nonrigid rotor model is developed from the two-parameter quantum algebra
$U_{qp}({\rm u}_2)$. [This model presents the $U_{qp}({\rm u}_2)$ symmetry and
shall be referred to as the qp-rotor model.] A rotational energy formula as
well as a qp-deformation of E2 reduced transition probabilities are derived.
The qp-rotor model is applied (through fitting procedures) to twenty rotational
bands of superdeformed nuclei in the $A \sim 130$, 150 and 190 mass regions.
Systematic comparisons between the qp-rotor model and the q-rotor model of
Raychev, Roussev and Smirnov, on one hand, and a basic three-parameter model,
on the other hand, are performed on energy spectra, on dynamical moments of
inertia and on B(E2) values. The physical signification of the deformation
parameters q and p is discussed.
