Achievement API for Windows 8

My google skills have failed miserably. If anyone would be able to point me to an acheivements/leaderboard API for use in the windows 8 store i would be very appreciative. I've found third party APIs to use xbox live achievements but they seem to be more for querying what acheivements you have for displaying on some website. I'm writing a game and would like to use (if possible) the MS sanctioned leaderboard and and acheivements API. something similar to the gamecenter api on ios.

any help appreciated. Thank you.