  We apply Tsallis's q-indexed nonextensive entropy to formulate a random
matrix theory (RMT), which may be suitable for systems with mixed
regular-chaotic dynamics. We consider the super-extensive regime of q < 1. We
obtain analytical expressions for the level-spacing distributions, which are
strictly valid for 2 \times 2 random-matrix ensembles, as usually done in the
standard RMT. We compare the results with spacing distributions, numerically
calculated for random matrix ensembles describing a harmonic oscillator
perturbed by Gaussian orthogonal and unitary ensembles.
