Rails looks for .rhtml even when rxml exists.

Hi

I am building XML using partials but for some (I cannot see a pattern
for when it happens) cases I get the:

No such file or directory /app/views/content_objects/news_article/xml/
partials/_show.rhtml

The corresponding rxml file /app/views/content_objects/news_article/
xml/partials/_show.rxml exists and I would like Rails to look for it
instead. For another case this works:

render :partial => "products/xml/partials/show", :locals =>
{:xml_instance => xml, :show => @product}

This finds the partial in /products/xml/partials/_show.rxml

Does anyone have any input on this? Am I doing something wrong in the
rendering? Is there a way to explicitly tell Rails which extension to
look for?

Kindest regards

Erik Lindblad