Simple variables for AdS$_5 \times S^5$ superspace

We introduce simple variables for describing the AdS$_5\times S^5$ superspace, i. e. $\frac{PSU(2,2|4)}{SO(4,1)\times SO(5)}$. The idea is to embed the coset superspace into a space described by variables which are in linear (ray) representations of the supergroup $PSU(2,2|4)$ by imposing certain supersymmetric quadratic constraints (up to two overall U(1) factors). The construction can be considered as a supersymmetric generalisation of the elementary realisations of the $AdS_5$ and the $S^5$ spaces by the SO(4,2) and SO(6) invariant quadratic constraints on two six-dimensional flat spaces.