Wie ändere ich den Hintergrund des Textes von "pic text" in einem tikzpicture?

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\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{angles,calc,positioning}
\begin{document}
  \begin{tikzpicture}[scale=3]
    \coordinate[label=270:$M$] (M) at (0,0);
    \draw (M) circle (1);
    \draw (0,0) -- (30:1) coordinate (Pi);
    \draw (0,0) -- (70:1) coordinate (Pi1);
    \coordinate (C) at ($(Pi)!0.5!(Pi1)$);% <- vor dem Zeichnen des Winkels
    \draw (M) -- (C);% <- vor dem Zeichnen des Winkels
    \pic [pic text=$\alpha$,draw,angle radius=1.2cm,
      pic text options={fill=white,inner sep=2pt}%<- weißer Hintergrund für α
      ]{angle=Pi--M--Pi1};
    \draw [red] (Pi) -- (Pi1) node[pos=0.5,above right] {$x$};
    \pic [pic text=$\ldotp$,draw,angle radius=0.3cm]{angle=M--C--Pi};
  \end{tikzpicture}
\end{document}
 
 
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