Problem with StringReader or TextAsset not reading some characters

My code:

 StringReader tr = null;
 TextAsset data = (TextAsset)Resources.Load("data.ext", typeof(TextAsset));
 tr = new StringReader(data.text);    
 sTemp = tr.ReadLine();
 Debug.Log(sTemp);

data.ext file:

 00!%%%£r!%%%£122222230e0e01255

My output:

 00!%%%r!%%%122222230e0e01255

As you can see StringReader (or possibly TextAsset) doesn't seem to like the £ character.

I have looked on the .net and unity docs, but I can't find any explanation.

Thanks for your help.