We present strong experimental evidence suggesting that we have synthesized the beta-C3N4 phase. This is a material predicted by theory to have bulk moduli comparable to diamond. Thin films containing small crystals were deposited on Si and Ge wafers by rf diode sputtering of a pure graphite target with pure N2. The crystal structure of these phases was investigated using x-ray and electron-beam diffractometry as well as transmission electron microscopy. Our results indicate that the beta-C3N4 particles with typical dimensions of approximately 0.5 mum are embedded in a 1-mum-thick layer of a C-N polymer. These particles are believed to crystallize preferentially on Si (100) wafers.