maybe you'll be lucky like me and your work will let you park your bike at your desk or inside your office :-)
also, find out if they will let you put it inside the loading dock area or something, so at least you're not leaving it out to the elements.
to your specific question, a U-lock through the seat tube and around the rear wheel, and a locking (non QR) front axle will be ok, just make sure you lock it something very secure.
the sad reality is that just this year, our local "cycling collective" has probably seen over a dozen bikes stolen, some VERY high end, and they were all locked. they were stolen in from various locations, at all time of day and night, sometimes taken from right out in the open during the daytime. thieves are thieves and they don't care. if they really want it, they will get it, no matter how good your lock is. at some point brute force and a few tools is going to win. I've even seen them unbolt sign posts and bike racks from the ground to slip the u lock off the post it is attached to . . .
the best advice is to buy a crappy "looking" commuter and don't put lots of name brand kit on it. keep your nice bike at home.