[CentOS] sed append question

Hey guys,
I am trying to make sed append every line containing a string with another line.
problem is the appended line needs to start with a tab:
# sed -i '/string/a \tstuff\t\t\tmorestuff' file
Obviously \t or \x09 etc doesn't get interpreted unless there are other characters
before it? How can I get this to begin with a <tab>?

Thanks!
jlc