  We report the observation of superconductivity in infinite-layer Ca-doped
LaNiO$_2$ (La$_{1-x}$Ca$_x$NiO$_2$) thin films and construct their phase
diagram. Unlike the metal-insulator transition in Nd- and Pr-based nickelates,
the undoped and underdoped La1-xCaxNiO2 thin films are entirely insulating from
300 K down to 2 K. A superconducting dome is observed at 0.15<x<0.3 with weakly
insulating behavior at the overdoped regime. Moreover, the sign of the Hall
coefficient $R_H$ changes at low temperature for samples with a higher doping
level. However, distinct from the Nd- and Pr-based nickelates, the
$R_H$-sign-change temperature remains at around 35 K as the doping increases,
which begs further theoretical and experimental investigation in order to
reveal the role of the 4f orbital to the (multi)band nature of the
superconducting nickelates. Our results also emphasize the significant role of
lattice correlation on the multiband structures of the infinite-layer
nickelates.
