Don't know how seam produces the EntityManager but the configuration is correct.
You can read about it here:

--- Eric Covener <> schrieb am Di, 28.6.2011:

Von: Eric Covener <>
Betreff: Re: OWB with Seam?
Datum: Dienstag, 28. Juni, 2011 22:49 Uhr

On Tue, Jun 28, 2011 at 4:30 PM, Thomas Andraschko
<> wrote:
> As you can see in the project uploaded at megaupload (it is linked in one of the older posts) the entitymanager is produced through seam with following producer field in my application:
> public class MyEntityManagerProducer {
>     @ExtensionManaged
>     @Produces
>     @PersistenceUnit
>     @ConversationScoped
>     EntityManagerFactory myEntityManagerFactory;
> }

I don't know anything about JPA, but this field produces a
EntityManagerFactory while you inject an EntityManager.  You'd need to
either uses a producer method that invokes the factory, or inject the
factory and then invoke it.