create new raster from raster using if statement in R

I have a raster layer showing SST during present, but only showing pixels where I know is suitable habitat for a species. All other pixels are set NA.

Now I have the same raster layer, but showing predicted SST for 2050. In this raster layer, all pixels have a value (except NA on land surfaces).

Now I want to do the following: I want to search the second raster layer for the values given in the first raster layer and set all other values 0. So the result should be a raster showing only pixels which have values that can also be found in the first raster.

I think the right function to use would be if else function.

Is there a way to use all values of a raster in an if else function? The code should be something like the following then:

    if(raster1@data@values==raster2){
      raster3 <- 1
      }else{
      raster3 <- 0
      }