What is the maximum memory Phantom4 Camera

Please elaborate ? What do you mean by 'maximum ;memory' ? The camera has no memory. Do you mena the SD-card ?

DJI recommend up to 64GB.
But using the biggest card you can get doesn't make much sense.
A 16 GB card will hold more than one full flight recording 4K video or many flights of stills.
If you value your images, you wouldn't store many flights all on the same card, and risking losing everything every time you fly.
Several 16GB cards is a much better solution.

Has anyone tried a card that is larger than 64Gb? I bought a 64Gb Sandisk card the day after I got my Phantom 4 (I got a great deal, £16) not realising that the 16Gb card that came with the P4 was plenty big enough.  The only time that 64Gb has come in handy is when I either forget or don't have time to transfer the footage to my laptop.

Hello q8_000, Labroides's answer is correct. Besides, here are 4 recommended cards for the Phantom 4:
1）        Lexar 633X Class10 16GB MicroSDHC UHS-I
2）        Panasonic 16GB MicroSDHC UHS-3
3）        Sandisk Extreme 16GB MicroSDHC UHS-3
4）        Lexar 633X Class10 64GB MicroSDXC UHS-3