$U_{\alpha 5}^{2}=U_{\alpha\beta}^{2}-\frac{d_{\alpha\gamma}d_{\alpha\delta}d_{%
\beta 5}}{d_{\alpha 5}}=U_{\beta\gamma}^{2}-\frac{d_{\alpha\beta}d_{\alpha%
\gamma}d_{\delta 5}}{d_{\alpha 5}}\neq 0,$