Error in recoding vars in R

I have imported from Excel a file that after being imported has the following str

str(mydata)
$ Injury   : chr  "MMCAI" "MMCAI" "MMCAI" "MMCAI" ...
$ Na_RR    : num  161 152 152 150 143 ...
$ place    : chr  "core" "core" "core" "core" ...

Now I want to create 5 different groups combining vars "Injury" and "place" I have this code

mydata$group[mydata$Injury=="MMCAI" & mydata$place=="core"]<- "IC"

However, after passing the code I got observations that are classified as NA i.e:

 231    core    MMCAI   138.8168    3.253879    core    IC
 232    core    MMCAI   142.7655    3.096850    core    NA
 233    core    MMCAI   141.1135    3.066894    core    NA
 234    core    MMCAI   137.1993    2.922434    core    NA
 235    core    MMCAI   138.3765    2.848378    core    NA

I cannot find the error... Any help will be greatly appreciated

Thanks