
\documentclass[border=5pt,multi=true]{standalone}
\usepackage{standalone}
\usepackage{ifthen}
\usepackage{threeparttable}
\usepackage{microtype}
\usepackage{lineno}
\usepackage{xspace}
\usepackage{caption}
\usepackage{graphicx}
\usepackage{color}
\usepackage{colortbl}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsfonts}
\usepackage{upgreek}
\usepackage{hyperxmp}
\usepackage{hyperref}
\usepackage{hypcap}
\usepackage{xspace}
\usepackage{upgreek}
\usepackage{cite}
\usepackage{mciteplus}
\usepackage{longtable}

\begin{document}
\small


  \begin{tabular}{ l |ll}
\hline
                &  $ S_f$ \xspace &  $ S_{\bar{f}}$ \xspace\\
\hline
 $ S_f$ \xspace           & $\phantom{-}1   $ & $-0.41   $  \\
 $ S_{\bar{f}}$ \xspace          & $-0.41   $ & $\phantom{-}1   $  \\
\hline
\end{tabular}
\end{document}
