New isotope, 264Sg, was identified using the 38U(30Si,xn)268-xSg reaction and excitation functions for 262-264Sg were measured. 264Sg decays by spontaneous fission with a half life of 37 +27/-11 ms. The spontaneous fission branch for 0.9-s 263Sg was measured for the first time and found to be (13+-8) percent. 262Sg decays by spontaneous fission with a 15 +5/-3 ms half-life. Spontaneous fission partial half-life systematics are evaluated for even-even Sg isotopes from 258Sg through 266Sg, spanning the transition region between the N=152, Z=100 and N=162, Z=108 deformed shells.