Searching for "atom podcast" finds me podcasts about atoms, which I'm sure are fascinating but are not what I'm looking for. I've built an RSS feed for a podcast, but I'd like to replace it with Atom, which seems to be better defined and more capable of including arbitrary HTML content.
Use an enclosure link (or multiple) in your entry subtree(s).
An overview of the Atom 1.0 Syndication Format has a nice side-by-side example of an RSS and Atom podcast feed.