radiation - What common materials absorb most infrared light?

I'm competing in a simple robotics competition where most of the participants use reflected infrared light to detect their opponent. I'd like to make my own robot as difficult to see as possible. What common materials (fabric, plastic, paint, etc) absorb most infrared light, and reflect as little of it as possible? I first thought any flat-black substance might do, but I've learned that what appears dark in the visible spectrum might still appear bright to infrared.

Answer

The common materials I found that best absorbed IR light are rubbery matte-black substances. Spray-on rubbery substances like Plastidip and Flexidip also worked well. But like pentane's answer explains, even these still reflect quite a lot.

Edit: Although it wasn't exactly what I was looking for, I found that, as far as IR sensors are concerned, most mirrors I tested seem to reflect most IR light. So if the goal is to confuse IR sensors, a mirror positioned at a 45 degree angle is better at effectively "absorbing" light than a matte black finish.