  Neutral kaon pairs produced in phi decays in anti-symmetric entangled state
can be exploited to search for violation of CPT symmetry and Lorentz
invariance. We present an analysis of the CP-violating process phi->K_S
K_L->pi+pi-pi+pi- based on 1.7 fb-1 of data collected by the KLOE experiment at
the Frascati phi-factory DAFNE. The data are used to perform a measurement of
the CPT-violating parameters Delta_amu for neutral kaons in the contest of the
Standard Model Extension framework. The parameters measured in the reference
frame of the fixed stars are: Delta_ao = (-6.0 +- 7.7_{stat} +- 3.1_{syst}) x
10^{-18} GeV Delta_ax = ( 0.9 +- 1.5_{stat} +- 0.6_{syst}) x 10^{-18} GeV
Delta_ay = (-2.0 +- 1.5_{stat} +- 0.5_{syst}) x 10^{-18} GeV Delta_az = ( 3.1
+- 1.7_{stat} +- 0.5_{syst}) x 10^{-18} GeV These are presently the most
precise measurements in the quark sector of the Standard Model Extension.
