We have searched for superconductivity in a wide variety of stoichiometries in the Y-Ni-B-C system, usingYx(NiB)Cyphase spread alloy thin films and the magnetic field modulated microwave absorption technique. The superconducting critical temperature(Tc)varies with the stoichiometry, showing the highestTcfor a Y/Ni ratio of 1/2, attributed to theYNi2B2Cphase. We found no other superconducting phases with aTchigher than 10 K. Furthermore, a search inYxNiB(C1−zNz)yandYxNiBNyphase spread alloys showed no superconductivity. ©1997 American Institute of Physics.