Automorphism groups of superextensions of groups

The superextension $\lambda (X)$ of a set $X$ consists of all maximal linked families on $X$. Any associative binary operation $\ast :X\times X\to X$ can be extended to an associative binary operation $*: \lambda(X)\times\lambda(X)\to\lambda(X)$. In the paper we study isomorphisms of superextensions of groups and prove that two groups are isomorphic if and only if their superextensions are isomorphic. Also we describe the automorphism groups of superextensions of all groups of cardinality $\le 5$.