Yahoo Chief Executive Marissa Mayer’s big media push is getting under way. On Monday, Katie Couric announced her official debut with Yahoo, slated for Friday with an interview with former New York City Mayor Michael Bloomberg. Couric is just one of a handful of high-profile journalists in a talent grab Mayer made recently — a list that also includes David Pogue, Matt Bai, and Megan Liberman. Pogue’s tech news site launched in January at the Consumer Electronics Show. Also in January, Couric released a test segment where she interviewed former Defense Secretary Robert Gates. Couric, appointed to a position called “Global Anchor” for Yahoo News, announced her debut, naturally, via Tumblr post. The chat with Bloomberg is his first public interview since he was appointed to the United Nations’ special envoy for cities and climate change.