Killing Heidi’s debut album, “Reflector,” will be one hard act to follow in its native Australia.

One of the fastest-selling albums in Australian history, “Reflector” entered the Down Under charts at No. 1, has gone quadruple-platinum and has yielded three Top 5 singles. Last fall, the rock quartet – led by photogenic 17-year-old singer Ella Hooper and her 20-year-old brother, guitarist Jesse – was named best new artist in Rolling Stone Australia’s readers poll, and the group snared four awards at the 14th annual SCAPE ARIA Awards, including album of the year and best group.

An even bigger challenge will be cracking the U.S. market, which hasn’t allowed an Australian invasion since the early 1980s. Jesse Hooper is crossing his fingers and hoping for the best after “Reflector” was issued stateside on March 20 on 3:33 Music Group/Universal.

“There’s been some killer acts that have come out of Australia over the years,” Hooper said recently, “but it’s not like it happens every year. It takes years for them to come out and evolve and for the public to take to them. Like AC/DC, it would be awesome to stick around that long and reach that stage where you’re so respected.

“But we’re still on our first record, and we’re having a ball. We’re having our first glimpse of the industry, so it’s still new and exciting for us. Hopefully, we’ll still be here as old rockers.”

Neither the Hoopers nor bassist Warren Jenkin and drummer Adam Pedretti could have anticipated such across-the-board success for “Reflector” back home.

“It’s crazy over here,” Jesse Hooper said. “We were hoping it would do well, but we had no idea it would end up on the mainstream charts. Our first single was on the alternative chart for six months without creeping over onto the mainstream chart. The next single, ‘Mascara,’ went No. 1, then the album came out a few months after that.

“We just couldn’t believe it, especially when you consider that there’s so much pop out there. Occasionally, there’s a good song on the charts, so it was wicked for us to reach so many people, especially when you compared it to all the pop from the Backstreet Boys and ‘N Sync.”

Endearing them even more to their fellow countrymen was the fact that “Mascara” was the first home-grown No. 1 in three years.

Their Seattle-style guitar rock was polished by producer Paul Kosky (Crowded House, The Clouds).

“It was our first record experience,” Jesse Hooper said, “and it took us six months to do it, because Ella and I were still in high school. We weren’t there in the studio every day. It was interesting to see how Paul made an album, with a slow, steady approach. I had a good time doing it that way, because it gave us time to focus on it. In the end, it was worth it, because we all got the album we love.”

It’s all a long way from the Hoopers’ hometown of Violet Town, a burg of 750 people in the northeast Victoria countryside. Their parents, both teachers, supported their rock ‘n’ roll pursuits but thought it was only a passing fancy.

“At first, we started playing around our local country area where we grew up,” Jesse Hooper said. “It was only when we got label interest and we won a demo contest in ’96 that our parents suddenly took an interest in our band a little bit more. They always had been interested and encouraging, but they thought what we were doing was more fun than something to do seriously. Now look at us.”

Hooper says he can’t predict how “Reflector” will do in the United States until they can do a proper tour stateside.

“It seems like ‘Mascara’ is being well-received and getting spins all around,” he said. “We just got to hope that builds up, so we can get back over there and capitalize on it.”

THE FIRST RECORD I EVER BOUGHT: ” ‘Siamese Dreams’ by Smashing Pumpkins. They were one of my favorite bands all through high school. That record, in particular, was one of their better ones. That’s the one that made me think, ‘Ah, yes, guitar heaven.’ ”

THE FIRST CONCERT I EVER WENT TO: “Push Over, a local festival in Melbourne in 1996. Silverchair was headlining, and Spider Base also played. It was a great show. We ended up playing at the same festival.”

MY MUSICAL HERO: “I have a few, but I really admire Billy Corgan a great deal and Maynard from Tool. His voice is amazing to me.”

BWF (before we forget): Killing Heidi goes in for the kill on the Web @ Other sites – and