Template friend function of template class that returns a reference to an implementation class object

I have this template function and class in mc.h/mc.cpp files:

template <class MemT>
class MC;

template <class MemT>
MemT & getMCObj(int t_instNum);

class HBM;

template <class MemT>
class MC
{
public:
    MC(){}

    friend MemT & getMCObj<MemT>(int t_instNum);

private:
    MemT memTobjList[12];
};

class HBM
{
public:
    bool someFunc();

private:
    int num_inst;
};

In the cpp file I have

template<class MemT>
MemT & getMCObj(int t_instNum)
{
    return MC<MemT>::memTobjList[t_instNum];
}

bool HBM::someFunc()
{
    num_inst = 1;
}

In main:

int main()
{
    MC<HBM> mC;


    HBM & ptr = getMCObj<HBM>(3);
    ptr.someFunc();

    return 0;
}

I get this error when I compile: main.cpp:8: undefined reference to `HBM& getMCObj(int)'

I can't seem to figure out whats going wrong. Whats the issue here?

Thanks.