2x2 symmetric tensor structure.
Rendering
\usepackage{tensormatrix}
$\begin{tmat}{2}{2} \tmatpv{1}{1} \tmatpv{1}{2} \tmatpv{2}{1} \tmatpv{2}{2} \tmatlink{1 1}{2 2} \end{tmat}$
tensormatrix
Tensor Matrix
Linked Elements