Through time-series CCD photometry of the globular cluster NGC 5466 , we have detected nine SX Phoenicis stars including three new ones .
All the SX Phoenicis stars are located in the blue straggler region in the color-magnitude diagram of NGC 5466 .
Five of them show clearly double-radial mode features , the periods of which are well consistent with the theoretical ratio of the first overtone mode to the fundamental mode ( P _ { 1 H } /P _ { F } ) .
Normally , it has not been easy to secure a P-L relation of the SX Phoenicis stars , because determination of the pulsational mode of the SX Phoenicis stars has been difficult .
The existence of five SX Phoenicis stars in NGC5466 with double-radial modes allows us to derive reliably a P-L relation for the fundamental mode of the SX Phoenicis stars .
Using seven SX Phoenicis stars including five stars with double-radial modes , we derive a P-L relation for the fundamental mode in NGC 5466 , < V > = -3.25 ( \pm 0.46 ) LogP + 14.70 ( \pm 0.06 ) ,~ { } ( \sigma = \pm 0.04 ) , corresponding to < M _ { V } > = -3.25 ( \pm 0.46 ) LogP - 1.30 ( \pm 0.06 ) 
for an adopted distance modulus of ( m - M ) _ { 0 } = 16.00 and zero reddening .