CA siteminder and SSO to SAP portal

I'm trying to set up an SAML 2.0 based SSO between the SAP portal (java 7.4) and CA siteminder.

I was following the instructions in

http://wiki.scn.sap.com/wiki/display/Security/Single+Sign-On+with+SAML+2.0+and+ABAP+Systems+Supporting+SAP+Logon+Tickets

and the metadata files were exchanged.

On the portal, the IDP seems to be active, however,when logging on to the portal the normal SAP user authentication comes up.

Any idea what could be the issue?

thanks