XML-error: Not well-formed (invalid token)

Hello,

I want a new XML structure in the Script from my InDesign CS6 (MAC 10.7.4) document. Here ist my little testscript:

     var doc = app.documents.item(0);
     var allStories = doc.stories;
    
    newXML = new XML('<root></root>');
    for(var i = 0; i < allStories.length; i++) {
        var curStory = allStories;
        
         for(var j = 0; j < curStory.textStyleRanges.length; j++) {
            var textStyleRange = curStory.textStyleRanges;
       
            alert(textStyleRange.contents);
            t = new XML('<content>' +textStyleRange.contents + '</content>');
            newXML.appendChild(t);
        }
    }
    alert(newXML);

The document has a text frame with the text, such as "C & A". When the script starts, it shows me the error message "XML-error: Not well-formed (invalid token)" on.

The problem with the "&" is. Probably also other Characters.

I think InDesign can automatically convert this into "&" or other entities, but how?