\footnote gives error in minipage environment with cta-author class

Question

I need to use \footnote in a minipage environment, but it always gives an error

Command \itshape invalid in math mode. a\footnote{

mwe is

\documentclass{cta-author}
\begin{document}

\begin{table}
\begin{minipage}{\columnwidth}
    \begin{tabular}{|c|c|}
        \hline
        Column 1 & Column2 \\
        a\footnote{footnote example} & b\\
        \hline
    \end{tabular}
\end{minipage}
\end{table}
\end{document}

Latex class file is here

Answer 1

You can redefine the way cta-author makes the footnote mark. Instead of $^{...}$, use \textsuperscript{...}:

\documentclass{cta-author}

\makeatletter
\def\@makefnmark{\textsuperscript{\@thefnmark}}
\makeatother

\begin{document}

\begin{table}
  \begin{minipage}{\columnwidth}
    \begin{tabular}{|c|c|}
      \hline
      Column 1 & Column2 \\
      a\footnote{footnote example} & b \\
      \hline
    \end{tabular}
  \end{minipage}
\end{table}

% A possible work-around
\begin{table}
  \begin{tabular}{|c|c|}
    \hline
    Column 1 & Column2 \\
    a$^*$ & b \\
    \hline
  \end{tabular}

  \medskip

  \footnoterule

  {\itshape\footnotesize $^*$footnote example}
\end{table}

\end{document}

And here is a visual of the work-around: