<<< native
[ ESqrt
    (EArray
       [ AlignCenter , AlignCenter ]
       [ [ [ EPhantom (EIdentifier "A") ]
         , [ EPhantom (EIdentifier "A") ]
         ]
       , [ [ EPhantom (EIdentifier "A") ]
         , [ EPhantom (EIdentifier "A") ]
         ]
       ])
]
>>> tex
\sqrt{\begin{matrix}
\phantom{A} & \phantom{A} \\
\phantom{A} & \phantom{A}
\end{matrix}}