If you mean to combine by mixing the two, it most certainly wouldn't
work. PMC has to be torch/kiln fired. Poly clay is oven bake and
emits toxic/acrid smoke and fumes when overbaked.
But, you can create a poly clay shape -- cab or freeform --- and set
it into PMC like any other material. Both must be baked/cured first.
You can't fire a poly cab in PMC like you can a lab-created stone.
Just remember if you bezel set your polymer that it's terribly soft
and will scratch.
Now, what you CAN do is create a PMC piece, then place your polymer
over it, bake the polymer to it's proper temp, and you'll have a
bead. Can't vouch for how successful the paring would be, but many
polymer artist incorporate metal wire their raw work. So it would
probably depend on the design. Something like a bead cap would
probably work OK.
There was an article I remember reading a while back about an artist
who uses polymer clay shapes and bonds them or sets them on her metal
work. They were called wild women pins (sorry, I couldn't find them
online). I think she glued in her polymer clay and seed beads and set
her gems in the traditional way. Very, very cool line.