I'm trying to draw the following diagram with the tikz-feynman
package.
\documentclass{standalone}
\usepackage{tikz-feynman}
\begin{document}
\begin{tikzpicture}
\begin{feynman}
\vertex [dot, label=180:$x$] (x) at (0,0) {};
\vertex [dot, label=0:$x'$] (y) at (2,0) {};
\vertex [dot, label=180:$x_1$] (x1) at (0,2) {};
\vertex [dot, label=0:$x_2$] (x2) at (2,2) {};
\diagram*{
(x1) -- [fermion, half left, out=45, in=135] (x2)
-- [fermion] (x)
-- [fermion] (y)
-- [fermion] (x1),
(x1) -- [photon] (x2),
};
\end{feynman}
\end{tikzpicture}
\end{document}
As you can see, the diagram has two fermion lines that intersect right in the middle, where their arrows are drawn. I would like to move the arrows along the fermion lines, so that the two ones don't overlap. How can I do this?