The corporate-rock breakthrough of brainy post-hardcore types At the Drive-In remains one of the most amazing rock phenomena of the past few years: like Nirvana before them, they were so kick-ass that they bowled over indie kids and new-metal knuckleheads alike. Also like Nirvana, they were too good to be true; the group called it quits just as their major-label debut, Relationship of Command (Grand Royal), was taking off. At the time, they said they were going on hiatus. But it wasn’t long before they announced a split into two factions: the Mars Volta, with frontman Cedric Bixler and guitarist Omar Rodriguez, and Sparta, with guitarist Jim Ward, bassist Paul Hinojos, and drummer Tony Hajjar.

At first glance, the Mars Volta might seem the bigger deal of the two. But Sparta are coming on strong out of the gate with a debut EP, Austere, on DreamWorks and an inaugural nationwide tour that hits the Middle East this Tuesday. The reconfigured line-up both looks and sounds like a stripped-down version of At the Drive-In: Ward does all the singing, Hinojos has switched over to guitar, and they’ve recruited bassist Matt Miller from their home town of El Paso.

"We’ve become even closer than we ever were," says Hajjar over the phone from El Paso. "I’ve never been happier than I am now, and it’s not because of who’s in the band or anything like that. It’s almost like the break-up made us grow up. We were in the same mindframe playing to 3000 people as we had been playing to two people. Your thinking has to change, and ours never did. So to get over it, in the sense of ‘Let’s fix the old problems and let’s continue doing what we enjoy doing,’ was a good feeling."

Austere ventures into territory both familiar and new to Sparta: the angular rock chorus of the opening "Mye" is as radio-ready as anything by their old band, but "Echodyne Harmonic (de-mix)" is a Radiohead-style excursion into breakbeat minimalism. "I became a lot niftier in my programming during our time off," says Hajjar. "I always wanted to push the electronic realm and then put our sense of rock into it. We really took it to an extreme. We’ve never had limits. Our fun begins with not caring if our song completely turns into an electronic song."

Sparta recently finished recording their debut full-length with superstar pop-punk producer Jerry Finn (Blink-182, Sum 41) — an alliance just as unlikely as the one At the Drive-In formed with new-metal visionary Ross Robinson (Korn, Limp Bizkit). "The thing is, we learned our lesson when we worked with Ross," says Hajjar. "Before we started, we were like, ‘Oh, we don’t wanna work with a guy that’s worked with those bands.’ You have to figure out your own experience with it. With Jerry, we just had breakfast with him one day. We talked about music for 10 minutes, and the rest of the time we made stupid jokes. That’s how we knew he was the right guy. It turned out that he has great ideas and really helped our record. It was a pleasure to work with him."

Sparta perform this Tuesday, April 9, at the Middle East, 480 Mass Ave in Central Square, with Thursday and Detachment Kit. It’s 18-plus, and tickets are $10. Call (617) 864-EAST.