BibTeX, biblatex and biber ⇒ \citealp in multibib + natbib... ?

[Medova]

Having set up the multibib together with natbib, I ran into a problem. If I want to cite the author, what do I the do...?
I want something like this:

\citet{jon90} --> Jones et al. [21]

I can't find any documentation for this together with multibib
(I am using bib-style "unsrt")