Aluminum for mains is common but I would say your application is not a main more of a sub panel off your main house service? I think you can get a 2-2-2-6 wire at lowes / HD for this the ground is a bit smaller than the conductors may be overkill but not sure what their next size is?. At 100' lay the pipe added protection if you can if not make sure your strap it so nothing can hit it later!
You need to look over at the Electrical forum. You'll get a lot of good info for sub panel feeds.
You can go with Aluminum 2-2-2-4 or 2-2-4-6 Mobile Home Feeder (MHF) and that will be good for up to 90A for your 100'. You need four conductors because an equipment ground is required to be run between the main and sub. The sub will require the addition of a ground bar because the ground and neutral are not bonded in the sub. The existing neutral/ ground bar in the sub will need to have the case bonding screw removed. And also you need to install two 8' ground rods 6' apart from each other connected by #6 bare copper to the ground bar in the sub.
For just 60A you can use #4 Al THHN/THWN or #6 Cu THHN/THWN.