Obrigado colega, mas já foi resolvido!
L1 <- c(1,2,4,5)
L2 <- c(7,2,1,5)
L3 <- c(9,3,1,5)
L4 <- c(6,2,1,5)
L5 <- c(5,2,1,4)
L6 <- c(9,2,1,5)
M = matrix(c(L1,L2,L3,L4,L5,L6),,4,byrow=T)
unique(t(apply(M,1,sort)))
T <- duplicated(t(apply(M,1,sort)),fromLast=FALSE)|duplicated(t(apply(M,1,sort)),fromLast=TRUE)
which(T)
Att.
André