[tannhaeuser]

I have taken a look at the .mdhtml file and don't know what you mean ;(

I you mean having one file that can contain both markdown and HTML, that's what markdown is already, since you can fallback to inline or block-level HTML in markdown.

If OTOH you want a HTML file that can also contain markdown (or other custom Wiki syntax, and text substitution variables, and a whole lot more), than that's available in SGML (on which HTML is based) via short references.