The present invention relates to a compound represented by the formula (1)
wherein Xa and Xb are each independently X1 or X2;
s is 1 or 2,
R4 is an alkyl group having 1-6 carbon atoms,
na and nb are each independently 0 or 1,
R1a and R1b are each independently an alkylene group having 1-6 carbon atoms,
R2a and R2b are each independently an alkylene group having 1-6 carbon atoms,
Ya and Yb are each independently an ester bond, an amide bond, a carbamate bond, an ether bond or a urea bond, and
R3a and R3b are each independently a sterol residue, a liposoluble vitamin residue or an aliphatic hydrocarbon group having 12-22 carbon atoms,
and use thereof.