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.

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Any idea what could be the issue?

thanks