Hi there. We were having the same problem, so I searched the 'Net extensively but kept finding the same answers: "I didn't get the medal either;" "There's no way to get the medal;" "You can't get the medal on this level no matter what."
Long story short, I finally stumbled upon one post that offers a solution, yet to be tested:
"Posted by ashburn247 on Oct 24, 2009 9:36 am PT
How do you get the medal of honor on operation market?
I have gone through it 2 times on authentic now and its the only level where it wont give it to me.
Posted by clippers1624 on Jun 19, 2010 1:37 pm PT
You need all Kilroys and Recon points and make sure you take out every german. Do not forget the upstairs of the farmhouse."
I'll edit/update this post after the theory has been tested!