Hi John,
thank you for your answer. It seems not to work:
[root@webbi /]# yum --enablerepo=sme7contribs --enablerepo=smecontribs install smeserver-phpmyadmin
Loaded plugins: fastestmirror, protect-packages, smeserver
Error getting repository data for sme7contribs, repository not found
[root@webbi /]#