We report a tentative detection with the IRAM 30m telescope of the LiH molecule in absorption in front of the lensed quasar B0218+357 .
We have searched for the J = 0 \rightarrow 1 rotational line of lithium hydride at 444 GHz ( redshifted to 263 GHz ) .
The line , if detected , is optically thin , very narrow , and corresponds to a column density of N ( LiH ) = 1.6 10 ^ { 12 } cm ^ { -2 } for an assumed excitation temperature of 15 K , or a relative abundance LiH/H _ { 2 } \sim 3 10 ^ { -12 } .
We discuss the implications of this result .