Trying to remove HTML layout from RXML templates

Hi you all,

I have a simple REST app with a controller method like this:
def index
    @sdrs = Sdr.find(:all)
    respond_to do |format|
      format.html
      format.xml
    end
end

The rxml is well constructed, however, what I get when the request is
through XML is the xml information surrounded by the layout of the app,
something like:
- <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
- <head>
    <meta http-equiv="content-type" content="text/html;charset=UTF-8" />
    <title>Sdrs: index</title>
   </head>
- <body>
   <p style="color: green" />

   <?xml version="1.0" encoding="UTF-8" ?>
- <sdrs>
- <sdr>
     <miliseg_ini>693710000</miliseg_ini>
     <miliseg_fin>62238000</miliseg_fin>
    </sdr>
   </sdrs>
  </body>
  </html>

How can I say that I just want the xml output?

Either this:
layout 'application', :except => :create_with_ajax
or this:
http://dev.rubyonrails.org/ticket/7682 (some code is in the middle of
the page)

-Christoph